• 디지털산업정보학회논문지
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• 제18권2호
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• pp.1-8
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• 2022

The message propagation between vehicles must be efficiently performed to quickly transmit information between vehicles in vehicle ad hoc networks (VANETs). Broadcasting can be the most effective solution for propagating these messages. However, broadcasting can cause broadcast storm problems, which can reduce the performance of the overall network. Therefore, rapid information delivery in VANET requires a method that can propagate messages quickly without causing the broadcast storm problems. This paper proposes a lightweight and opportunistic broadcast (LOB) protocol that leverages the features of opportunistic routing to propagate messages quickly while minimizing the load on the network in VANETs where the network topology changes frequently. LOB does not require any routing information like greedy forwarding scheme, and neighboring nodes at the farthest distance within the range of transmission nodes are likely to be selected as forwarding nodes, and multiple forwarding candidate nodes like opportunistic routing scheme can increase packet transmission rates. Simulation results using ns-2 showed that LOB outperformed existing broadcast protocols in terms of packet rate and packet delay.

• 한국정보과학회논문지:정보통신
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• 제35권2호
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• pp.120-129
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• 2008

정보 수집이 목적인 센서 네트워크에서 자신의 전력을 절약하기 위해 다른 노드들의 패킷을 의도적으로 전송하지 않는 이기적인 노드가 포함되어 있을 수 있다. 이를 해결하기 위해 크레딧을 이용한 패킷 전송에 따른 지불 방법을 제안하였다. 센서 노드들이 패킷을 전송할 때, 크레딧을 사용하게 하고, 다른 노드들의 패킷을 전송하는 것을 통해 크레딧을 얻을 수 있게 하였다. 크레딧의 신뢰성을 보장하기 위해서 싱크 노드와 서버의 역할을 통합하고 piggybacking 기법을 이용하여 추가적인 리포트 메시지를 송신하지 않도록 하였다. 또 위치상의 이유로 다른 노드들이 전송하는 패킷을 받지 못하여 크레딧을 얻지 못하는 노드를 찾아 크레딧을 추가 지급함으로써 부당하게 대우를 받는 문제를 해결하였다. 제안된 방법의 성능 평가를 위하여 네트워크 시뮬레이션(ns2)를 이용하여 구현하였으며. 실험 결과, 이기적인 노드를 처리하기 위해 패킷 지불 방식만을 이용한 것보다 패킷 전송률이 높게 유지되었고, 시뮬레이션 시간 내 도착된 패킷의 총 개수 또한 증가하였다. 그리고 센서 노드의 전력 소모량이 줄어들어 노드들이 살아 있는 시간이 길어짐을 확인할 수 있었다.

• Journal of Information Processing Systems
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• 제9권3호
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• pp.477-488
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• 2013

Wireless Sensor Networks (WSNs) are comprised of sensor nodes that forward data in the shape of packets inside a network. Proficient packet forwarding is a prerequisite in sensor networks since many tasks in the network, together with redundancy evaluation and localization, depend upon the methods of packet forwarding. With the motivation to develop a fault tolerant packet forwarding scheme a Self-Localized Packet Forwarding Algorithm (SLPFA) to control redundancy in WSNs is proposed in this paper. The proposed algorithm infuses the aspects of the gossip protocol for forwarding packets and the end to end performance of the proposed algorithm is evaluated for different values of node densities in the same deployment area by means of simulations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제12권9호
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• pp.4271-4294
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• 2018

Communication cost is the most important factor in Wireless Sensor Networks (WSNs), as exchanging control keying messages consumes a large amount of energy from the constituent sensor nodes. Time-based Dynamic Keying and En-Route Filtering (TICK) can reduce the communication costs by utilizing local time values of the en-route nodes to generate one-time dynamic keys that are used to encrypt reports in a manner that further avoids the regular keying or re-keying of messages. Although TICK is more energy efficient, it employs no re-encryption operation strategy that cannot determine whether a healthy report might be considered as malicious if the clock drift between the source node and the forwarding node is too large. Secure SOurce-BAsed Loose Synchronization (SOBAS) employs a selective encryption en-route in which fixed nodes are selected to re-encrypt the data. Therefore, the selection of encryption nodes is non-adaptive, and the dynamic network conditions (i.e., The residual energy of en-route nodes, hop count, and false positive rate) are also not focused in SOBAS. We propose an energy efficient selection of re-encryption nodes based on fuzzy logic. Simulation results indicate that the proposed method achieves better energy conservation at the en-route nodes along the path when compared to TICK and SOBAS.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권2호
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• pp.234-252
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• 2013

Due to the uncertain of connections in Delay Tolerant Networks (DTNs), most routing algorithms in DTNs need nodes to forward the message to others based on the opportunistic contact. The contact is related with the beaconing rate. In particular, nodes have more chances to encounter with each other with bigger beaconing rate, but more energy will be used. On the other hand, if the nodes forward the message to every node all the time, the efficiency of the routing algorithm is better, but it needs more energy, too. This paper tries to exploit the optimal beaconing rate and forwarding rate when the total energy is constraint. First, a theoretical framework is proposed, which can be used to evaluate the performance with different forwarding rate and beaconing rate. Then, this paper formulates a joint optimization problem based on the framework. Through Pontryagin's Maximal Principle, this paper obtains the optimal policy and proves that both the optimal forwarding and beaconing rates conform to threshold form. Simulation results show the accuracy of the theoretical framework. Extensive numerical results show that the optimal policy obtained in this paper is the best.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권4호
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• pp.973-988
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• 2012

Delay tolerant networks (DTNs) characterized by the lack of guaranteed end-to-end paths exploit opportunistic data forwarding mechanism, which depends on the hypothesis that nodes are willing to store, carry, and forward the in-transit messages in an opportunistic way. However, this hypothesis might easily be violated by the presence of selfish nodes constrained with energy, bandwidth, and processing power. To address this problem, we propose a practical reputation-based incentive scheme, named PRI, to stimulate honest forwarding and discipline selfish behavior. A novel concept of successful forwarding credential and an observation protocol are presented to cope with the detection of nodes' behavior, and a reputation model is proposed to determine egoistic individuals. The simulation results demonstrate the effectiveness and practicality of our proposal.

• Journal of Communications and Networks
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• 제16권4호
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• pp.465-474
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• 2014

Wireless sensor network (WSN) is considered to be one of the most important research fields for ubiquitous healthcare (u-healthcare) applications. Healthcare systems combined with WSNs have only been introduced by several pioneering researchers. However, most researchers collect physiological data from medical nodes located at static locations and transmit them within a limited communication range between a base station and the medical nodes. In these healthcare systems, the network link can be easily broken owing to the movement of the object nodes. To overcome this issue, in this study, the fast link exchange minimum cost forwarding (FLE-MCF) routing protocol is proposed. This protocol allows real-time multi-hop communication in a healthcare system based on WSN. The protocol is designed for a multi-hop sensor network to rapidly restore the network link when it is broken. The performance of the proposed FLE-MCF protocol is compared with that of a modified minimum cost forwarding (MMCF) protocol. The FLE-MCF protocol shows a good packet delivery rate from/to a fast moving object in a WSN. The designed wearable platform utilizes an adaptive linear prediction filter to reduce the motion artifacts in the original electrocardiogram (ECG) signal. Two filter algorithms used for baseline drift removal are evaluated to check whether real-time execution is possible on our wearable platform. The experiment results shows that the ECG signal filtered by adaptive linear prediction filter recovers from the distorted ECG signal efficiently.

• 한국통신학회논문지
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• 제37권8B호
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• pp.712-721
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• 2012

본 논문에서는 무선 센서 네트워크에서 프로토콜 성능 극대화를 위해서 비동기식 MAC과 라우팅 교차 계층 방식의 향상된 위치 기반 데이터 전송 (Enhanced Geographic Forwarding; EGF) 기법을 제안한다. EGF 기법은 기존의 일반적인 위치 기반 전송 알고리즘과 달리 주기적인 이웃 노드들의 위치 정보 등을 이용하지 않고, 오직 소스와 목적지 노드의 위치 정보와 에너지 비용 정보만을 이용한 최적의 back-off 매핑 메커니즘을 사용하여 데이터를 전송한다. 또한 효율적인 MAC과 라우팅의 교차 계층 방식으로 오버헤드를 최소화하고 데이터 전달 성능을 최적화 하였다. 성능 분석 결과 패킷 전송 성공률, 저전력성 및 데이터 전송 지연에 대해서 향상된 성능을 확인하였다.

• International Journal of Computer Science & Network Security
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• 제21권3호
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• pp.165-171
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• 2021

Vehicular Ad hoc Network (VANET) is an extension paradigm of moving vehicles to communicate with wireless transmission devices within a certain geographical limit without any fixed infrastructure. The vehicles have most important participation in this model is usually positioned quite dimly within the certain radio range. Fuzzy based multi-hop broadcast protocol is better than conventional message dissemination techniques in high-mobility VANETs, is proposed in this research work. Generally, in a transmission range the existing number of nodes is obstacle for rebroadcasting that can be improved by reducing number of intermediate forwarding points. The proposed protocol stresses on transmission of emergency message projection by utilization subset of surrounding nodes with consideration of three metrics: inter-vehicle distance, node density and signal strength. The proposed protocol is fuzzy MHB. The method assessment is accomplished in OMNeT++, SUMO and MATLAB environment to prove the efficiency of it.

• 한국멀티미디어학회논문지
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• 제10권1호
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• pp.13-25
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• 2007

그리드 데이터베이스에서는 질의 전달 최적화를 위해 캐쉬를 사용한다. 캐쉬에 빈번히 사용되는 데이터의 메타 정보를 메타 데이터베이스에서 가져와 캐싱하며, 캐싱된 정보를 통하여 질의 전달의 비용을 감소시킨다. 기존의 캐쉬 관리 기법은 질의 전달 시 복제본의 사용빈도를 고려하지 않은 데이터의 임의의 메타 정보를 캐싱하기 때문에 사용이 불균형적인 문제가 있다. 그리고, 원본 데이터가 변경되었을 경우에 기존의 메타정보를 가진 캐쉬를 통하여 질의가 타 노드로 잘못 전달되며 이러한 과정은 여러 노드에서 반복 수행되어 네트워크 비용을 증가시킨다. 따라서 기존의 캐쉬 관리 기법은 복제본의 사용비율 불균형과 타 노드로의 잘못된 질의 전달로 인한 네트워크 비용 증가 문제의 해결이 필요하다. 본 논문에서는 질의 전달 최적화를 위한 캐쉬 관리 기법을 제안한다. 제안 기법은 캐쉬 매니저라는 관리 프로세서를 사용하여 캐쉬를 관리한다. 캐쉬 매니저는 자주 사용되는 복제본이 저장된 노드의 사용빈도를 비교하여 적게 사용된 노드의 복제본 메타 정보를 캐싱함으로써 질의 전달을 최적화한다. 또한 캐쉬 매니저를 통해 타 노드로 잘못 전달되는 질의를 줄여 질의 처리 시간을 단축하고 네트워크 비용을 줄인다. 제안 기법은 성능평가를 통해 네트워크 비용과 처리시간이 감소되어 기존의 방식에 비하여 향상된 성능을 보인다.