• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권12호
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• pp.5729-5744
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• 2017

Vehicular Ad Hoc Networks (VANET) in the large-scale road section usually have typical characteristics of large number of vehicles and unevenly distribution over geographic spaces. These two inherent characteristics lead to the unsatisfactory performance of VANETs. This poor performance is mainly due to fragile communication link and low dissemination efficiency. We propose a novel routing mechanism to address the issue in the paper, which includes a competition-based routing discovery with priority metrics and a local routing repair strategy. In the routing discovery stage, the algorithm uses adaptive scheme to select a stable route by the priorities of routing metrics, which are the length of each hop, as well as the residual lifetime of each link. Comparisons of different ratios over link length and link stability further show outstanding improvements. In the routing repair process, upstream and downstream nodes also compete for the right to establish repair process and to remain as a member of the active route after repair. Our simulation results confirm the improved performance of the proposed algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권5호
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• pp.1929-1950
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• 2020

Reliable and secure data transmission in the application environment assisted by the wireless sensor network is one of the major challenges. Problem like blind forwarding and data inaccessibility affect the efficiency of overall infrastructure performance. This paper proposes routing protocol for forwarding and error recovery during packet loss. The same is achieved by energy and hops distance-based formulation of the routing mechanism. The reachability of the intermediate node to the source node is the major factor that helps in improving the lifetime of the network. On the other hand, intelligent hop selection increases the reliability over continuous data transmission. The number of hop count is factor of hop weight and available energy of the node. The comparison over the previous state of the art using QualNet-7.4 network simulator shows the effectiveness of proposed work in terms of overall energy conservation of network and reliable data delivery. The simulation results also show the elimination of blind forwarding and data inaccessibility.

• 한국지능시스템학회논문지
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• 제20권1호
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• pp.36-41
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• 2010

무선 센서 네트워크의 효율적인 에너지 사용과 개별 노드의 수명 증대는 센서 네트워크의 효율적인 운영을 위한 매우 중요한 요소이다. 센서 네트워크에 많이 사용되는 LEACH, HEED 등과 같은 클러스터 기반의 라우팅 방식들은 클러스터 헤드들과 해당 멤버 노드들 간의 데이터 전달을 통하여 에너지의 효율성을 얻는다. 본 논문에서는 대표적인 클러스터 기반 라우팅 방식인 LEACH와 HEED의 방법을 비교분석하고 데드 노드의 최대 지연 발생 등과 같은 새로운 에너지 효율적인 클러스터 헤드 선출 방법을 제안한다. 제안된 방법의 효율성은 MATLAB 시뮬레이션을 통해 확인하였다.

• 정보처리학회논문지C
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• 제12C권6호
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• pp.875-880
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• 2005

제한된 자원을 가진 센서 노드들로 구성된 센서 네트워크에서 가장 중요한 이슈 중 하나는 쑤어진 에너지를 최대한 활용하여 네트워크 수명을 연장하는 것이다. 네트워크 수명을 연장하는 가장 대표적인 방법은 클러스터링 방법이다. 본 논문에서는 CH(Cluster Head) 및 후보 CH 노드들로부터 주어지는 통신 부하(load)와 잔여 에너지 양에 대한 정보를 기반으로 클러스터 크기를 동적으로 변화시켜 클러스터 내의 노드 밀도에 상관없이 각 CH에게 주어지는 부담을 일정하게 유지시키는 새로운 동적 크기 다중홉 클러스터링 방법을 제안한다. 시뮬레이션을 통해 제안된 방법이 기존의 단일홉 모드나 고정 크기 다중홉 모드 클러스터링 방법보다 우수함을 보였다.

• 한국공간정보시스템학회 논문지
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• 제12권1호
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• pp.1-9
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• 2010

최근, 무선 센서 네트워크 기술은 유비쿼터스 컴퓨팅 시대의 핵심 기반 기술의 하나로 인식되고 있다. 센서 노드는 제한된 배터리 용량을 가지기 때문에, 장기간 생존하기 위해서 노드들의 동작에 적은 에너지를 소모해야한다. 따라서, 에너지를 효율적으로 사용하는 프로토콜이 필수적이다. 이를 위해 본 논문 에서는 에너지 사용량을 고려하여 에너지 소모가 적은 경로를 설정하는 위치 기반의 에너지 효율적인 라우팅 프로토콜을 제안한다. 아울러 메시지 전송이 원활하지 못한 경우를 처리하는 경로 재설정 알고리즘을 제안한다. 마지막으로 TOSSIM을 이용한 성능평가를 통해, 제안한 프로토콜이 에너지 효율성 측면에서 기존 위치기반 라우팅 프로토콜 보다 우수함을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제3권2호
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• pp.209-218
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• 2009

In a wireless sensor network(WSN) each sensor node deals with numerous sensing data elements. For the sake of energy efficiency and network lifetime, sensing data must be handled effectively. A technique used for this is data aggregation. Sending/receiving data involves numerous steps such as MAC layer control packet handshakes and route path setup, and these steps consume energy. Because these steps are involved in all data communication, the total cost increases are related to the counts of data sent/received. Therefore, many studies have proposed sending combined data, which is known as data aggregation. Very effective methods to aggregate sensing data have been suggested, but there is no means of deciding how long the sensor node should wait for aggregation. This is a very important issue, because the wait time affects the total communication cost and data reliability. There are two types of data aggregation; the data counting method and the time waiting method. However, each has weaknesses in terms of the delay. A hybrid method can be adopted to alleviate these problems. But, it cannot provide an optimal point of aggregation. In this paper, we suggest a stochastic-based data aggregation scheme, which provides the cost(in terms of communication and delay) optimal aggregation point. We present numerical analysis and results.

• 융합신호처리학회논문지
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• 제15권4호
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• pp.155-161
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• 2014

본 논문에서는 비교적 밀도가 높게 전개되는 무선 센서네트워크에서 센서노드들의 에너지를 균형있게 소비할 수 있는 클러스터-기반 에너지 소비 균형을 위한 라우팅 프로토콜을 제안하였다. 본 프로토콜은 계층적 구조를 가지는 클러스터-기반으로 구현된다. 클러스터는 위치적으로 가까운 거리에 있는 센서노드들로 형성되며, 해당 클러스터 멤버들 중에서 잔류 에너지가 가장 높은 노드가 헤드노드로 선정된다. 경로 선정에서, 이웃하는 클러스터와 통신의 범위가 중첩되게 하여 그 공통영역 내에 있는 하나의 노드를 중계노드로 선택하여, 통신에너지 소비의 균형을 고려하여 노드들의 수명을 연장할 수 있게 하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.285-288
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• 2001

In this paper we proposed the on line volt/var control schemes of the load Tap Changer (LTC) transformer and shunt capacitor bank for distribution volt/var regulation. In the existing volt/var control of the distribution substation, the voltage of feeders and var of distribution systems is mainly controlled by the LTC transformer tap position and on/off status of the shunt capacitor. The LTC and shunt capacitor bank has discrete operation characteristics and therefore it is very difficult to control volt/var at the distribution networks within the satisfactory levels. Also there is limitation of the operation times of the LTC and shunt capacitor bank because it is affects on their functional lifetime. The proposed volt/var control algorithm determine an optimal tap position of LTC and on/off status of shunt capacitors at a distribution network with the multiple feeders. The mathematical equations of the proposed method are introduced. Simple case study was performed to verify the effectiveness of the proposed method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 A
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• pp.399-402
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• 2003

In this paper, the on line volt/var control algorithms of the food Load Tap Changer (LTC) transformer and Shunt Capacitor(SC) are proposed for distribution volt/var regulation. In the existing volt/var control of the distribution substation, the voltage of feeders and var of distribution systems is mainly controlled by the LTC transformer tap position and on/off status of the shunt capacitor. The LTC and shunt capacitor bank has discrete operation characteristics and therefore it is very difficult to control volt/var at the distribution networks within the satisfactory levels. Also there is limitation of the operation times of the LTC and shunt capacitor bank because it is affects on their functional lifetime. The proposed volt/var control algorithm determine an optimal tap position of LTC and on/off status of shunt capacitors at a distribution network with the multiple feeders. The mathematical equations of the proposed method are introduced. Simple case study was performed to verify the effectiveness of the proposed method.

• 대한산업공학회지
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• 제29권4호
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• pp.312-320
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• 2003

Recently there is a growing interest in mobile cellular network providing multimedia service. However, the link bandwidth of mobile cellular network is not sufficient enough to provide satisfactory services to users. To overcome this problem, an adaptive framework has been proposed. In this study, we propose a new method of estimating DPR(Degradation Period Ratio) in an adaptive multimedia network where the bandwidth of ongoing call can be dynamically adjusted during its lifetime. DPR is a QoS(Quality of Service) parameter which represents the ratio of allocated bandwidth below a pre-defined target to the whole service time of a call. We improve estimation method of DPR using DTMC(Discrete Time Markov Chain) model by calculate mean degradation period, degradation probability more precisely than in existing studies. Under Threshold CAC(Call Admission Control) algorithm, we present analytically how to guarantee QoS to users and illustrate the method by numerical examples. The proposed method is expected to be used as one of CAC schemes in guaranteeing predefined QoS level of DPR.