• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.4
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• pp.728-738
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• 2016

We are currently able to share not only the information from humans but also the data from connected things on the Internet. We are getting close to IoT era because of progress of Information Communication Technology. Therefore, the ways of data transfer are offered between things to things. One of typical way is the HTTP protocol. However, The field of Internet of Things platforms requires more fast and more stable communication protocol to handle massive data. The system supporting HTTP protocol, there is a problem of transmission efficiency in a relatively large header compared to data. also HTTP protocol system overload situations and the problem of data compatibility happens due to each standard of many organizations. Thus, To solve these problems, I suggest the data collection solution based on MQTT protocol for the operation of the stable IoT platforms.

• 한국정보통신설비학회:학술대회논문집
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• 2009.08a
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• pp.157-161
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• 2009

In recent years, there is a remarkable progress in ICTs (Information and Communication Technologies), and then many attempts to apply ICTs to other industries are being made. In the field of disaster managements, ICTs such as RFID (Radio Frequency IDentification) and USN (Ubiquitous Sensor Network) are used to provide safe environments. Actually, various types of early warning systems using USN are now widely used to monitor natural disasters such as floods, landslides and earthquakes, and also to detect human-caused disasters such as fires, explosions and collapses. These early warning systems issue alarms rapidly when a disaster is detected or an event exceeds prescribed thresholds, and furthermore deliver alarm messages to disaster managers and citizens. In general, these systems consist of a number of various sensors and measure real-time stream data, which requires an efficient and rapid data processing technique. In this study, an event-driven architecture (EDA) is presented to collect event effectively and to provide an alert rapidly. A publish/subscribe event processing method to process simple event is introduced. Additionally, a complex event processing (CEP) technique is introduced to process complex data from various sensors and to provide prompt and reasonable decision supports when many disasters happen simultaneously. A basic concept of CEP technique is presented and the advantages of the technique in disaster management are also discussed. Then, how the main processing methods of CEP such as aggregation, correlation, and filtering can be applied to disaster management is considered. Finally, an example of flood forecasting and early alarm system in which CEP is incorporated is presented It is found that the CEP based on the EDA will provide an efficient early warning method when disaster happens.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.6
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• pp.215-221
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• 2011

Communication infrastructure of wireless sensor networks significantly tends to depend on application requirements. Gossip communication is becoming one of the promising solutions for addressing its scalability problems in providing information propagation functionality based on the P (publish)/S (subscribe) paradigm. In particular, despite the importance of both guaranteeing message delivery order required and supporting overlapping groups in sensor networks, there exist little research works on development of gossip-style dissemination protocols to satisfy all these requirements. In this paper, we present the latest causal information transmission protocol between publishers and subscribers for overlapping groups. In this protocol, sensor leaders as publishers might guarantee consistently causally ordered message delivery among themselves by aggregating causality information. On the other hand, only the latest causal information piggybacked on each multicast message is transmitted from publishers to subscribers through gossip-style dissemination. Its scalability feature might be highly suitable for the area of the applications requiring only the minimum meaningful information.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.5
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• pp.231-237
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• 2017

This paper presents an implementation of a smart flowerpot which can adjust humidity and illumination automatically after monitoring the temperature, humidity, and illumination. We made a container of the flowerpot with a 3D printer and embedded a NodeMCU micro controller in it. We attached a temperature sensor, a humidity sensor, an illumination sensor, and a water pump to the NodeMCU. We developed a control program that adjusts humidity and illumination and ran it on the NodeMCU. Also we developed an Android application and set up an MQTT server. Using the MQTT server, the NodeMCU and the Android application can exchange messages which keep sensor values and commands. Using the Android application. the user can send the proper temperature, humidity, and illumination to the smart flowerpot and monitor the sensor values.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.12 no.9
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• pp.4103-4121
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• 2018

Quality of Service (QoS) awareness is recognized as a key point for the success of Internet of Things (IOT).Realizing the full potential of the Internet of Things requires, a real-time task scheduling algorithm must be designed to meet the QoS need. In order to schedule tasks with diverse QoS requirements in cloud environment efficiently, we propose a task scheduling strategy based on dynamic priority and load balancing (DPLB) in this paper. The dynamic priority consisted of task value density and the urgency of the task execution, the priority is increased over time to insure that each task can be implemented in time. The scheduling decision variable is composed of time attractiveness considered earliest completion time (ECT) and load brightness considered load status information which by obtain from each virtual machine by topic-based publish/subscribe mechanism. Then sorting tasks by priority and first schedule the task with highest priority to the virtual machine in feasible VMs group which satisfy the QoS requirements of task with maximal. Finally, after this patch tasks are scheduled over, the task migration manager will start work to reduce the load balancing degree.The experimental results show that, compared with the Min-Min, Max-Min, WRR, GAs, and HBB-LB algorithm, the DPLB is more effective, it reduces the Makespan, balances the load of VMs, augments the success completed ratio of tasks before deadline and raises the profit of cloud service per second.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.4
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• pp.46-58
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• 2008

Naval combat management system is a kind of complex weapon systems performing naval ship's warfare mission by integrating various types of system including sensor systems, weapon systems and many kinds of communication system. Recently, there are many studies to apply commercial high-level communication middleware to naval combat system development to integrate and interoperate various kinds of heterogeneous on-board systems efficiently. An initial discovery mechanism is required for application modules to start communication with their relevant modules to apply middlware technology in developing naval combat system, which is characterized by large-scale, complex and real-time system. This paper suggests a fast hybrid discovery mechanism which combines static and dynamic discovery mechanism and confirms its adaptability by an experiment on testing environment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2017.10a
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• pp.533-535
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• 2017

MQTT provides three QoS levels on top of the TCP/IP layer to ensure message delivery reliability. However, in an environment where messages are concurrently transmitted and received in a node, messages are lost due to the delivery method for QoS level. In this paper, it construct an experimental environment in which MQTT generates concurrently messages, and confirm the message reliability according to QoS level. Therefore, we analyze the message reception ratio on the subscriber side by changing number of publisher and transmission cycle of message. Experimental results show that the message reception ratio of 1 and 2 except QoS level 0 decreases as the number of publisher increases or the message transmission cycle increases.

• International Journal of Computer Science & Network Security
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• v.21 no.11
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• pp.301-311
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• 2021

The technological advancements of the last two decades directed the era of the Internet of Things (IoT). IoT enables billions of devices to connect through the internet and share their information and resources on a global level. These devices can be anything, from smartphones to embedded sensors. The main purpose of IoT is to make devices capable of achieving the desired goal with minimal to no human intervention. Although it hascome as a social and economic blessing, it still brought forward many security risks. This paper focuses on providing a survey of the most commonly used application layer protocols in the IoT domain, namely, Constrained Application Protocol (CoAP), Message Queuing Telemetry Transport (MQTT), Advanced Message Queuing Protocol (AMQP), and Extensible Messaging and Presence Protocol (XMPP). MQTT, AMQP, and XMPP use TCP for device-to-device communication, while CoAP utilizes UDP to achieve this purpose. MQTT and AMQP are based on a publish/subscribe model, CoAP uses the request/reply model for its structuring. In addition to this, the quality of service provision of MQTT, AMQP, and CoAP is not very high, especially when the deliverance of messages is concerned. The selection of protocols for each application is very a tedious task.This survey discusses the architectures, advantages, disadvantages, and applications of each of these protocols. The main contribution of this work is to describe each of the aforementioned application protocols in detail as well as providing their thorough comparative analysis. This survey will be helpful to the developers in selecting the protocol ideal for their system and/or application.

• Journal of the Korea Society of Computer and Information
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• v.14 no.7
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• pp.123-132
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• 2009

The perforrnance and portability of mobile applications can be greatly increased by adopting proxy modiles which exists between the conventional system and the device. When mobile devices collaborate with the conventional computers, there are problems to address: a battery life problem, limited input and output methods, and intermittent wireless connection. Those issues are magnified in the multimedia collaboration environment since it works in a real-time condition and the size of the message in the system is big in many cases. Additionally, because multimedia collaboration system softwares are too heavy and complex for mobile devices, it is veη hard to integrate them with conventional systems. In this paper, we describe our design and its implementation of a novel approach to map events (i.e. messages) using a proxy for mobile applications. We adopt a proxy to provide a content adaptation (i.e. transcoding) where the message contents are customized. Also, we design a mobile version publish/subscribe system to provide communication service for mobile device in loosely coupled and flexible manner. We present our empirical results which show that our design can be efficiently implemented and integrated with a conventional multimedia collaboration system.

• Smart Media Journal
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• v.13 no.4
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• pp.76-85
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• 2024

In this paper, we propose a system that improves the data integrity of IoT(Internet of Things) devices in the virtual environment by combining Hyperledger Indy and MQTT(Message Queuing Telemetry Transport). The system complements the limitations of the centralized system by realizing a DPKI(Decentralized Public Key Infrastructure) structure that utilizes a distributed network in publish-subscribe(pub/sub) pattern communication. Digital signature technology was applied to ensure the data integrity of IoT devices and communication scenarios between the four core components of the client, IoT device, broker, and blockchain, as well as a topic structure using a decentralized identifier to ensure safety in the virtual environment. We present a systematic method for transparent data exchange. To prove the performance of the proposed system, this paper conducted experiments on four scenarios and evaluated communication performance in a virtual environment. The experimental results confirmed that the proposed system provides a reliable IoT data communication structure in a virtual environment.