• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.4
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• pp.7-12
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• 2014

IETF (Internet Engineering Task Force) CoAP (Constrained Application Protocol) protocol is supported communication between sensor or actuator nodes by in a constrained environment, such as small amount of memory, and low power. CoAP and HTTP protocol can convert easily, and can use to monitor or controll the infrastructure utility through low-power sensor and actuator networks in IoT (Internet of Thing) and M2M (Machine-to-Machine) environment. IETF CoRE(Constrained RESTful environments) Working Group proposed CoAP protocol in 2010, and began to standardize it. Recently, CoAP protocol is published RFC (Request for Comments) 7252. In this paper, we design and implement of CoAP protocol for testing the interoperability in heterogeneous operating environments. For this experiment, we developed the CoAP client program based on Windows environment and CoAP server program in Linux environment to test the interoperability.

• Convergence Security Journal
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• v.17 no.5
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• pp.3-10
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• 2017

Standard Protocol Optimized for Resource-Constrained IoT Environment Constrained Application Protocol (CoAP) supports web-based communication between a sensor node in the IoT environment and a client on the Internet. The CoAP is a Request / Response model that responds to the client's CoAP Request message by responding with a CoAP Response message from the server. CoAP recommends the use of CoAP-DTLS for message protection. However, validation of the use of DTLS in the IoT environment is underway. We analyze CoAP and DTLS security mode, evaluate performance of secure channel creation time, security channel creation step time, and RAM / ROM consumption through Cooja simulator and evaluate the possibility of real environment application.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.1
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• pp.147-153
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• 2016

Recently, IETF (Internet Engineering Task) working group has adopted CoAP (Constrained Application Protocol) as a standard IoT proctocol. CoAP is a specialized web transfer protocol for use with constrained nodes and constrained environment such as small memory and low power networks. In this paper, we design and implement a registration service with CoAP protocol based on RD(Resource Directory) to connect IoT nodes in mobile Internet environments. The resource directory between the mobile terminal and IoT nodes provides to discover the IoT nodes and get the context data. The mobile terminal has as the CoAP client and embedded IoT nodes includes as the CoAP server so that it can conveniently manage the constrained IoT nodes to get the context data and control devices in a mobile environments.

• Journal of the Korea Society of Computer and Information
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• v.21 no.1
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• pp.79-84
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• 2016

In this paper, we propose reliable message transmission scheme based on CoAP, considering the constrained feature of IoT device, such as low power, the limited memory size and low computing capacity. Recently, the various kinds of application protocol has been studied to support IoT environments. In particular, CoAP protocol was developed as application protocol for IoT at the IETF core WG. However, because CoAP protocol is deigned to be used in constrained node, this protocol uses UDP at transport layer. Thus, data loss may occur frequently in network congestion environments. The proposed scheme, in this paper, is to overcome the problem of frequent data loss with low overhead. Also it includes the function which is to minimize the data loss in sleep mode of IoT device.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.1
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• pp.17-26
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• 2019

The Constrained Application Protocol (CoAP) is a specialized web transfer protocol proposed by the IETF for use in IoT environments. CoAP was designed as a lightweight machine-to-machine protocol for resource constrained environments. Due to the strength of low overhead, the number of CoAP devices is expected to rise rapidly. When CoAP runs over UDP for wireless sensor networks, CoAP needs to support congestion control mechanisms. Since the default CoAP defines a minimal mechanism for congestion control, several schemes to improve the mechanism have been proposed. To keep CoAP lightweight, the majority of the schemes have been focused mainly on how to measure RTT accurately and how to set RTO adaptively according to network conditions, but other approaches such as rate-based congestion control were proposed more recently. In this paper, we survey the literature on congestion control for CoAP and discuss the future research directions.

• Proceedings of the Korean Society of Computer Information Conference
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• 2015.01a
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• pp.243-246
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• 2015

최근 사물 인터넷(Internet of things) 의 발달에 따라, 스마트 디바이스 간의 네트워크 및 이를 구축할 수 있는 기술에 대한 수요가 급증하고 있다. 이러한 스마트 디바이스 간의 저 전력 저 손실 네트워크(Low power and Lossy network) 환경에서 쓰이는 대표적인 프로토콜로 CoAP(Constrained Application Protocol)가 있으며, 해당 프로토콜은 다양한 네트워크 환경에 유연하게 적용할 수 있도록 패킷 재전송 주기 설정 옵션을 가진다. 하지만 하나의 디바이스에서 네트워크 환경이 패킷 손실 및 지연여부를 구분 할 수 없기 때문에, 네트워크 상태 파악을 위해서는 수신과 응답 양측 디바이스의 패킷 흐름을 확인해야 하는 문제점이 있다. 본 논문에서는 프로토콜의 정보를 기반으로 네트워크 상태를 파악 할 수 있는 새로운 필드 값을 적용하여 CoAP 패킷 재전송 주기를 네트워크 환경의 상태에 따라 동적으로 설정해주는 알고리즘을 제안한다. 제안된 기법은 동적으로 재전송 주기를 설정함으로써, 패킷 손실에 의한 서비스 장애 극복 및 패킷 지연 상황에서의 불필요한 패킷 재전송을 방지하여 에너지 효율성을 향상시키고 서비스 안정성을 보장한다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.15 no.6
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• pp.123-128
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• 2015

Recently, a communication protocol for connectivity between various sensors and actuators is issue the key technology in IoT(Internet of Things). IETF(Internet Engineering Task Force) CoAP(Constrained Application Protocol) protocol supports the communication between things like sensors and actuator nodes in a limited environment. Smart-phone will work for the data processing of the sensors and the management of IoT nodes at the next generation communication environment. In this paper, we design the connection for smart-phone and IoT node based using IETF CoAP protocol, and implement the middleware with the proposed data refinement on smart-phone. The middleware detects and eliminates a error data and duplicated data using the proposed data refinement. The proposed data refinement scheme supports to transfer a reliability information in the constrained environment.

• Journal of information and communication convergence engineering
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• v.9 no.5
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• pp.602-606
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• 2011

It is necessary for developing specific application protocol for mobile sensor end nodes and data collection devices that have constrained resources and computing powers. Because of these needs, IETF WG developed CoAP protocol and Internet draft was released, and processing to international standardization of this protocol. Because sensor nodes and information collection devices have restricted resources and computing powers, there are some limitations for applying to this proposed protocol directly. Thus in this paper we shows the implementation of full CoAP protocol for server, works on Linux and CoAP-Lite over telos which works on TinyOS for information collection devices. In this implementation we verified the main activities of CoAP protocol over USN by modifying some hardware with dependent algorithm.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.47-48
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• 2015

As the power system develops rapidly into a smarter and more flexible state, so must the communication technologies that support it. Machine to machine (M2M) communication in Smart Grid environment has been discussed in European Telecommunications Standards Institute (ETSI). The power system is not easily replaceable, due to system replacement cost. The M2M gateway is required in other to improve interoperability in M2M environment. The Distributed Network Protocol 3.0 (DNP3.0) is the most important standard in the SCADA systems for the power. It has been used for device data collection/control in Substation Systems, Distribution Automation System. If the DNP3.0 data model is combined with a set of contemporary web protocols, it can result in a major shift. We selected Constrained Application Protocol (CoAP) based on RESTful as M2M protocol. It is a specialized web transfer protocol for use with constrained nodes and constrained networks. We have used the OPNET Modeler 17.1 in order to verity the SOAP versus CoAP. In this paper, we propose the CoAP-based M2M Gateway to Distribution Automation system using DNP3.0 in Smart Grid Environment.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.2
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• pp.119-126
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• 2017

Developing the TCP/IP standard IBA which is higher organization of IETF decided to attach the TCP/IP protocol stack to small things, such as sensor. This means small object is also considered as on of the communication node, it has symbolic meaning that expand smart object has all five layer. Under this background, IoT/WoT configure the intelligent network between objects based on the internet to communication was introduced. Things has own IP address on IoT environment and are smart object that a lot of people communicate over the internet on Application Layer. In other words, IoT is that smart object are commercialized space. According to the interest of IoT, IETF establish CoAP for use as IoT protocol. CoAP is expected that standard protocols created by things is connected to the Internet protocol that can be used within a constrained environment. Accordingly, in this paper, we proposed Middleware API that can manage and collect the data of objects that connected CoAP network.