CCDC: A Congestion Control Technique for Duty Cycling WSN MAC Protocols

( Beakcheol Jang ),( Wonyong Yoon ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.8

Wireless Sensor Networks hold the limelight because of significant potential for distributed sensing of large geographical areas. The radio duty cycling mechanism that turns off the radio periodically is necessary for the energy conservation, but it deteriorates the network congestion when the traffic load is high, which increases the packet loss and the delay too. Although many papers for WSNs have tried to mitigate network congestion, none of them has mentioned the congestion problem caused by the radio duty cycling of MAC protocols. In this paper, we present a simple and efficient congestion control technique that operates on the radio duty cycling MAC protocol. It detects the congestion by checking the current queue size. If it detects the congestion, it extends the network capacity by adding supplementary wakeup times. Simulation results show that our proposed scheme highly reduces the packet loss and the delay.

무선 센서 네트워크를 위한 잔여 수명 기반 클러스터링 통신 프로토콜

장백철(Jang, Beakcheol) 한국산학기술학회 2014 한국산학기술학회논문지 Vol.15 No.4

무선 센서 네트워크는 넓은 지역을 위한 분산 센싱 시스템을 구현하는 데에 큰 잠재성을 가지고 있다.각 센서의 배터리 교환이 대체로 어렵다고 생각되기 때문에,무선 센서 네트워크의 수명 향상은 매우 중요한 연구 주제 이다.클러스터 링 방식은 각 각의 센서 노드가 패킷을 원거리의 싱크 노드에게 보낼 필요 없이,가까운 거리의 클러스터 헤드에게 보내면 되므로 에너지 효율적이다.이 논문에서 우리는 잔여수명을 기반으로 클러스터 헤드를 선정하는 무선 센서네트워크를 위한 클러스터링 통신 프로토콜을 제안 한다.우리가 제안한 알고리즘을 평가하기 위해,대표적인 무선 센서네트워크 클러스터링 알고리즘 중의 하나인 LEACH와 그 성능을 비교 한다.실험 결과는 우리의 알고리즘이 LEACH보다 트래픽 양 측면에서 20% ~ 30%,그리고 확장성 특면에서 30% ~ 40% 만큼 노드들의 평균 수명을 향상 시킨다는 것을 보여 준다. Wireless sensor networks (WSNs) have a big potential for distributed sensing for large geographical area. The improvement of the lifetime of WSNs is the important research topic because it is considered to be difficult to change batteries of sensor nodes. Clustering communication protocols are energy-efficient because each sensor node can send its packet to the cluster head near from itself rather than the sink far from itself. In this paper, we present an energy-efficient clustering communication protocol, which chooses cluster heads based on the expected residual lifetime of each sensor node. Simulation results show that our proposed scheme increases average lifetimes of sensor nodes as much as 20% to 30% in terms of the traffic quantity and as much as 30% to 40% in terms of the scalability compared to the existing clustering communication protocol, LEACH.

An Analysis of Indoor Positioning Technologies using Wireless Signals

Choi, Min-Seok,Jang, Beakcheol 한국컴퓨터정보학회 2016 韓國컴퓨터情報學會論文誌 Vol.21 No.6

In this paper, we present indoor positioning technologies using the wireless signal categorizing them into triangulation based, fingerprinting based, and cell ID based technologies. We describe several representative techniques for each of them emphasizing their strengths and weaknesses. We define important performance issues for indoor positioning technologies and analyze recent technologies according to the performance issues. We believe that this paper provide wise view and necessary information for recent indoor positioning technologies using wireless signals.

트위터 데이터를 위한 효과적인 단어 임베딩

김인환(Inhwan Kim),장백철(Beakcheol Jang) 한국통신학회 2018 韓國通信學會論文誌 Vol.43 No.11

Performance Evaluations of Text Ranking Algorithms

Myung-Hwi Kim(김명휘),Beakcheol Jang(장백철) 한국컴퓨터정보학회 2020 韓國컴퓨터情報學會論文誌 Vol.25 No.2

텍스트 순위 알고리즘은 키워드 추출을 위한 대표적인 방법이며 그 중요성이 강조되고 있다. 본 논문에서는 텍스트 랭킹 알고리즘에서 대표적으로 사용되는 TF-IDF, SMART, INQUERY, CCA 알고리즘이 적용된 최근 연구와 실험해 비교한다. 먼저, 각 알고리즘을 설명한 후 뉴스와 트위터 데이터를 기반으로 알고리즘의 성능을 분석한다. 실험 결과에 따르면 네 가지 알고리즘 모두 뉴스 데이터에서 특정 단어의 추출 성능이 좋다는 것을 알 수 있다. 그러나 Twitter의 경우 CCA는 특정 단어를 추출하는 최고의 성능을 가지며 INQUERY는 가장 낮은 성능을 보여준다. 또한 6 가지 비교 메트릭을 통해 알고리즘의 정확성을 분석한다. 실험 결과 CCA가 뉴스 데이터에서 최고의 정확도를 보여주고, 트위터의 경우 TF-IDF와 CCA는 비슷한 성능을 보이며 높은 정확도를 보인다. The text ranking algorithm is a representative method for keyword extraction, and its importance is emphasized highly. In this paper, we compare the performance of recent research and experiments with TF-IDF, SMART, INQUERY and CCA algorithms, which are used in text ranking algorithm. After explaining each algorithm, we compare the performance of each algorithm based on the data collected from news and Twitter. Experimental results show that all of four algorithms can extract specific words from news data equally. However, in the case of Twitter, CCA has the best performance to extract specific words, and INQUERY shows the worst performance. We also analyze the accuracy of the algorithm through six comparison metrics. The experimental results present that CCA shows the best accuracy in the news data. In case of Twitter, TF-IDF and CCA show similar performance and demonstrate good performance.

AP들의 상대적 세기를 통한 랜드마크 맵 구축과 이를 이용한 실내 위치 추적 기술

김현중(Hyunjung Kim),장백철(Beakcheol Jang) 한국컴퓨터정보학회 2020 韓國컴퓨터情報學會論文誌 Vol.25 No.1

본 논문에서는 상대적인 액세스 포인트의 신호 강도에 기초한 랜드마크를 사용하는 실내 위치 추적 기법에 대하여 제안한다. AP 신호의 절댓값은 기존의 실내 위치 추적 기술에 사용되었지만, 측정기기, 측정 환경, 그리고 측정 시기의 변동으로 인해 달라질 수 있다. 그러나 우리는 특정 장소에서는 AP의 수신 신호 세기의 흐름이 서의 일정한 패턴을 나타낸다는 사실을 알아냈다. 그 특징에 따라, 우리는 AP들 간의 상대적 강도를 파악하고, 그들이 특정 패턴을 보이는 특정 장소를 랜드마크로서 저장한다. 랜드마크 맵 배치가 완료되면, 시스템은 스마트폰의 IMU 센서를 사용하여 사용자의 위치를 계산하고 저장된 랜드마크로 보정한다. 우리의 시스템은 센서만 사용한 기술에 비하여 75.2%의 개선을, 그리고 절댓값으로 선택된 랜드마크를 사용한 기술에 비하여 39.6%의 개선을 보인다. In this paper, we propose an indoor positioning technique using the landmark based on relative Access Point (AP) signal strengths. The absolute values of AP signals are used to conventional indoor positioning technologies, but they may be different because of the difference of the measuring device, the measuring environment, and the timing of the measurements. However, we found the fact that the flow of the AP’s RSSI in certain places shows almost constant patterns. Based on theses characteristics, we identify the relative strength between the APs and store the certain places as landmarks where they show certain patterns. Once the deployment of the landmark map is complete, system calculate position of user using the IMU sensor of smartphone and calibrate it with stored landmarks. Our system shows 75.2% improvement over technology that used only sensors, and 39.6% improvement over technology that used landmarks that were selected with absolute values.

트위터와 단어 임베딩을 사용한 인플루엔자 감지

김인환(Inhwan Kim),장백철(Beakcheol Jang) 한국통신학회 2020 韓國通信學會論文誌 Vol.45 No.1

Cloud System Security Technology Trend

Jeong-Won Yoon,Beakcheol Jang 한국컴퓨터정보학회 2015 韓國컴퓨터情報學會論文誌 Vol.20 No.7

In this paper, we introduce recent cloud system security technologies categorizing them according to Reliability, Availability, Serviceability, Integrity, and Security (RASIS), terms that evaluate robustness of the computer system. Then we describe examples of security attacks and corresponding security technologies for each of them. We introduce security technologies based on Software Defined Network (SDN) for Reliability, security technologies based on hypervisor and virtualization for Availability, disaster restoration systems for Serviceability, authorization and access control technologies for Integrity, and encryption algorithms for Security. We believe that this paper provide wise view and necessary information for recent cloud system security technologies.

상용 실내 내비게이션 시스템 기술 동향

서재민(Jae-Min Seo),장백철(Beakcheol Jang) 한국컴퓨터정보학회 2017 韓國컴퓨터情報學會論文誌 Vol.22 No.1

In this paper, we introduce commercial indoor navigation systems being deployed and serviced in many fields of industry focusing on their indoor positioning technologies. Indoor positioning technology is a technology that locates people or targets in the interior of a building. To do that, it utilizes radio waves such as WiFi, and bluetooth, magnetic fields, or other sensory information from smart phones. We present indoor navigation systems categorizing them into their indoor positioning technologies. We define important performance issues for indoor positioning technologies and analyze them according to the performance issues. We believe that this paper provide wise view and necessary information for recent indoor navigation systems.

Open Hardware Platforms for Internet of Things : Evaluation & Analysis

Seo, Jae-Yeon,Kim, Myung-Hwi,Jang, Beakcheol 한국컴퓨터정보학회 2017 韓國컴퓨터情報學會論文誌 Vol.22 No.8

In this paper, we present open hardware platforms for Internet of Things (IoTs) emphasizing their strengths and weaknesses. We introduce six representative platforms, Raspberry PI, Arduino, Garileo, Edison, Beagle board and Artik. We define important performance issues for open hardware platforms for IoTs and analyze recent platforms according to the performance issues. We present recent research project using open hardware platforms introduced in this paper. We believe that this paper provide wise view and necessary information for open hardware platforms for Internet of Things (IoT).