Ki-Dong Nam

A gateway based fog computing architecture for wireless sensors and actuator networks

The technologies of Internet of Things have been wide used in many areas such as intelligent building, logistics, security, and health. One of the key elements of the Internet of Things is Wireless Sensors and Actuators Networks(WSANs). Fog computing, the new concept of the cloud at the edge of the network, is considered the appropriate platform for many Internet of Things services and applications. In this paper we present a gateway based fog computing architecture for WSANs and argue that the key requirements of this architecture. This architecture mainly consists of master nodes and slave nodes, and manages virtual gateway functions, flows, and resources.

Quality-based event reliability protocol in wireless sensor networks

For reliable event detection in wireless sensor networks, a sink requires collective information reported by sensor nodes sensing an event. In other words, the sink has to receive a certain amount of data dealing with the event for reliable event detection. Existing studies propose quantity-based event reliability protocols that improve event reliability by increasing the number of data successfully transmitted by controlling transport process. These studies present diverse schemes to successfully transmit as many reporting data as possible such as diversification of routing path for congestion avoidance and control of data reporting frequency rate for transport error compensation. However, since it frequently happens that wireless sensor networks with restricted capacity cannot deliver more than required amount of data due to data collision and congestion, the quantity-based event reliability protocols have limitation to raise the possibility of event detection. In this paper, we proposes a Quality-based Event Reliability Protocol (QERP) utilizing a property that the reporting data from sensor nodes are different in the contribution degree (CD) for event detection according to their environmental conditions. QERP selects sensor nodes to send their reporting data according to CD, and differentially transports them by CD-based buffer management and load balancing. Simulation results show that QERP detect more reliably and energy-efficiently an event than quantity-based event reliability protocols.

Real-Time Routing Protocol Based on Expect Grids for Mobile Sinks in Wireless Sensor Networks

Real-time data delivery is the most important requirement for mission-critical applications in wireless sensor networks. Since a mobile sink is requested for applications and for energy efficiency in WSNs, an Expect Area-based Real-time Routing protocol (EAR2) is proposed to support real-time routing to the mobile sink. EAR2 is based on an Expect Area (EA) of the mobile sink and exploit flooding of real-time data within EA. However, flooding within EA makes sensor nodes in EA consume much energy. Flooding time within EA may also be difficult to measure and change widely according to time and environment. Thus, to avoid the flooding problems in EAR2, we propose a new real-time routing protocol based on grids for a mobile sink. In addition to EA of a mobile sink, the proposed protocol considers Expect Grids (EGs) of the mobile sink, which are included in EA. Instead of flooding within EA, the proposed protocol exploits multicasting to EGs and one-hop forwarding in a EG because in comparison with flooding, multicasting saves much energy and one-hop forwarding time is easy to measure and changes narrowly according to time and environment. Simulation results show that the proposed protocol is superior to other protocols.

Reliable continuous objects detection algorithm in wireless sensor networks

In wireless sensor networks, reliable event detection is one of the most important research issues. For the reliable event detection, existing studies usually assume that events are individual objects such as tanks, people, and animals. The existing studies estimate detection reliability of an individual object by the ratio of the number of successfully received data packets at a sink to the number of data packets determined by applications for reliable detection. Recently, detection of the other one kind of events, called the continuous object, such as wild fire and bio-chemical material has been receiving increased attention. Unlike the individual objects, a continuous object might cover a wide area and it could dynamically alter its own shape according to physical environments, e.g. wind, geographical features, and so on. Hence, the continuous object detection reliability can not be estimated by the indicator for the individual objects. In this paper we newly define the reliability indicator for continuous object detection. Then, we propose error recovery and revision scheme based on the estimation result from the novel indicator. Simulation results prove that the proposed scheme provides high reliability with respect to continuous object detection.

Time synchronization method of network testing system by standard wave

The time synchronization is very important for network testing that is at a long distance. For time synchronization, two different network testing apparatuses uses a network time protocol (NTP) or a geographic position system (GPS). For using GPS with less timing error, an expensive GPS antenna needs to be installed outside the door. NTP is through the network. The network itself causes a time delay and the error in the time delay of the network occurs. So, NTP has not been used to measure a high speed network. This paper has been made in an effort to provide a network testing system using a Standard Wave to facilitate time synchronization with at least two network testing apparatuses, and an operating method thereof. The Standard Wave has extremely little time error. It helps to perform accurate testing.

Reliability Support Protocol for Continuous Object Detection in Large-Scale Wireless Sensor Networks

Recently, detection schemes of specific phenomena, called continuous objects, such as wild fire and bio-chemical material have been actively studied. A continuous object might cover a wide area and it could dynamically change its own shape according to physical environments, e.g. wind and geographical features. For continuous object detection, the schemes have focused on detection of the current boundary shape of a continuous object at a time period. However, the schemes merely aim at reducing communication costs for boundary information collection, but they do not take into account reliable information transport. Hence, we propose a Reliable Boundary Information Transport (RBIT) protocol for continuous object detection. The protocol is composed of three major mechanisms: 1) explicit Representative Boundary Node (RBN) election, 2) cluster-based boundary information loss recovery, and 3) cluster-by-cluster packet loss recovery. The explicit RBN is considered in order to estimate boundary information loss due to the dynamic property of continuous objects. The protocol then constructs coarse-grained grid clusters, and it allocates a header node per each cluster. The header node collects location information of RBNs in its own cluster and revises lost boundary information. By the clustering the protocol distributively manages all RBNs of the large-scale continuous object. Finally, cluster-by-cluster packet loss recovery is provided for end-to-end reliable transmission from a header node to a sink. The cluster-by-cluster loss recovery fills up lost packets by data packet retransmission between clusters.

Reliable Multicast Push Engine for Framing Transfer Design and Implement

The Push technology is the technology coming into the spotlight as the new service of an internet.. We study to graft the multicast technology for to the utmost reducing the load of an internet with the push technology. We propose to order data with framing and build the reliable multicast based upon this through the new method called a stamp. The push engine and sender, and the simple protocol between each other of a receiver were designed for a thing. Each application was actually implemented. The new multicast push engine is proposed based upon an experiment and implementation.