• Proceedings of the Korea Information Processing Society Conference
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• 2008.05a
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• pp.881-884
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• 2008

수중 음향 센서 네트워크는 무선 센서 네트워크의 한 분야로서 활발하게 연구되고 있다. 하지만 무선 센서 네트워크에서의 지상이라는 환경은 수중 음향 센서 네트워크에서의 수중이라는 환경과 많은 차이가 있다. 예를 들어 수중에서는 지상에서 보다 더 많은 통신 에너지를 필요로 하며 현재 단일채널 밖에 사용할 수 없다. 그러므로 수중 음향 센서 네트워크에서 무선 센서 네트워크의 메커니즘을 그대로 사용하기에는 적합하지 않다. 본 논문에서는 수중 음향 센서 네트워크에서의 에너지 효율적 클러스터링 메커니즘을 제안한다. 제안하는 클러스터링 메커니즘은 단일채널의 수중환경을 대상으로 클러스터 내 통신에서 발생하는 충돌문제를 최소화하여 에너지 효율을 증가시키기 위해 하향식방법을 이용하여 클러스터 헤드 노드를 선정하고 선정된 클러스터 헤드 노드를 중심으로 클러스터 범위를 결정하는 방법을 제시한다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.05a
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• pp.250-253
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• 2010

Underwater sensor network has attracted more and more attention from the networking research community recently. Most of traditional studies focus on the topology with a single gateway. Underwater sensor network consists of a variable number of sensors and multi-gateway to ensure the reliability of the network. In this paper, we propose a new MAC protocol that can reduce collisions among sensor nodes and improve QoS(Quality of Service) for underwater sensor network with multi-gateway. We evaluate the performance of the proposed scheme through simulation. Simulation results show that the proposed scheme outperforms the existing MAC protocol.

• Journal of the Korea Society for Simulation
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• v.20 no.4
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• pp.157-166
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• 2011

As underwater environment monitoring system's interest has increased, the research is proceeding about underwater acoustic sensor network. Underwater sensor network can be applicable to many fields, such as underwater environment monitoring, underwater resource exploration, oceanic data collection, military purposes, etc. It is essential to define the PHY-MAC protocol for revitalization of the underwater acoustic sensor network which is available utilization in a variety of fields. However, underwater acoustic sensor network has to implement by consideration of underwater environmental characteristics, such as limited bandwidth, multi-path, fading, long propagation delay caused by low acoustic speed. In this paper, we define frequency of adjusted PHY protocol, network topology, MAC protocol, PHY-MAC interface, data frame format by consideration of underwater environmental characteristics. We also present system configuration of our implementation and evaluate performance based on our implementation with test in real underwater field.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.87-89
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• 2011

전 세계적으로 수중 또는 해양의 정보는 매우 중요하며 다양한 활용가치를 지닌다. 수중 또는 해양을 개발하고 활용하기 위해서는 실시간으로 지속적으로 모니터링하면서 데이터를 수집하고 필요에 따라 수중 장치나 장비를 제어하는 기술이 기본적으로 요구된다. 본 논문에서는 수중 센서네트워크에 특징에 대해서 알아보고 클러스터링을 적용한 수중 네트워크내의 전송 효율 향상에 대해 연구하고, 통신을 위하여 MAC 계층으로 협업 통신을 적용하는 가능성 그리고 몇 가지 주의점에 대하여 알아보았다. 본 연구를 통하여 수중 네트워크로의 협업 통신 적용은 큰 가능성을 지니고 있으며, 지상에서와의 다른 환경 때문에 프로토콜의 적절한 설계가 매우 필요하다는 것을 알았다.

• Information and Communications Magazine
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• v.24 no.10
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• pp.34-43
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• 2007

해양은 육지, 공중과 같이 매우 중요한 국방전술 대상으로 수중 통신은 물론 수중과 지상을 연결하는 네트워킹 기술이 요구된다. 본 고에서는 해양에서 국방전술통신에 도입하기 위한 수중 센서 네트워크 시스템 기술에 대해 소개하며 이를 위해 해양 환경 분석과 더불어 해양에 알맞은 수중 센서 네트워크 시스템 모델을 제시하고 모델 각 구성요소의 기능에 대해 소개한다. 또한, 각 구성요소 기술 개발에 필요한 통신 프로토콜 계층 별 요구사항과 필요 연구를 소개하고 국내외 기술개발 동향에 대해 살펴본다.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.11 no.4
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• pp.17-22
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• 2011

The underwater environments are quite different from the terrestrial ones in terms of the communication channel and constrains. In underwater wireless sensor network, the probability of node failure is high because sensor nodes are deployed in more harsh environments than the ground based networks and moved by waves and currents. There are researches considering the communication environments of underwater to improve the data transmission throughput. In this paper, we present a checkpointing scheme of the cluster heads that recoveries from a cluster head failure quickly. Experimental results show that the proposed scheme enhances the reliability of the networks and more efficient in terms of the energy consumption and the recovery latency than without checkpointing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.7B
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• pp.886-891
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• 2011

Multicast has been a key routing service for efficient data dissemination in underwater acoustic sensor networks. In sensor networks, there are several multicast routing protocol which reflects sensor network nature. However, existing routing scheme was not targeted at underwater acoustic sensor networks which is hard to provide battery continually. Therefore, a specialized routing algorithm is essential for acoustic sensor networks. In this paper, we propose angle aided multicast routing algorithm for decreasing routing computation complexity, including virtual Euclidean Steiner point. Simulation results show better performance than exist routing Position Based Multicast, Geographic Multicast Routing. such as low computation capability and limited power consumption.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.3
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• pp.19-25
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• 2012

Underwater sensor networks (UWSNs) employ acoustic channels for communications. One of the main characteristics of the underwater acoustic channel is long propagation delay. Previously proposed MAC (medium access control) protocols for wireless sensor networks cannot be directly used in UWSNs due to the long propagation delay. The long propagation delay and uneven nodes deployments cause spatial fairness in UWSNs. Therefore, a new MAC protocol for UWSNs needs to be developed to provide efficient communications. In this paper, we propose an efficient MAC protocol in order to alleviate the fairness problem. In the proposed scheme, when a node receives a RTS packet, it does not immediately send back but delays a CTS packet. The node collects several RTS packets from source nodes during the delay time. It chooses one of the RTS packets based on the queue status information. And then, it sends a CTS packet to the source node which sent the chosen RTS packet. The performance of the proposed scheme is investigated via simulation. Simulation results show that our scheme is effective and alleviates the fairness problem.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.633-636
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• 2011

The paper deals with the performance of contention-based medium access control (MAC) protocols for underwater sensor networks. We extensively analyze the number of received-packets and the end-to-end delay of ALOHA, CSMA, CSMA-RTS-CTS and CSMA-RTS-CTS-ACK protocols using a Qualnet underwater network simulator which accommodates diverse underwater acoustic channel environments. Using simulation results, we support an engineering table to determine an adequate contention-based MAC protocol for underwater sensor networks.

• Journal of Advanced Marine Engineering and Technology
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• v.39 no.3
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• pp.268-273
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• 2015

Recently many countries are researching actively underwater sensor networks for securing ocean resources and changes of ocean environment in all over the world. Current the commercial modem are not suitable because it has characteristics of long distance, higher price, larger power consumption with the special object mainly. In this paper, a low power and compact underwater communication modem which is suitable for underwater sensor networks is implemented. It is comprised by using a simple analog circuit for non-coherent BFSK modulation method, ultra low power MCU and orthogonal codes with a less operation and a simple implementation. It was experimented an underwater communication using our modem in a water tank and open sea farms. It communicates fewer than $10^{-4}$ bit error rate.