• Journal of the Korea Society for Simulation
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• v.18 no.4
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• pp.175-184
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• 2009

The distance of sensor nodes is an important factor in having influence on capability of networks in underwater acoustic sensor networks. Our proposed scheme is to establish an efficient distance to design a route of communication in underwater environment and it proposes a Level scheme that the areas divided by transmit/receive distance in network are given different levels. Our proposed scheme is pursued research to maintain a established route and maximize an energy efficiency. The established route will have fluid modification by an internal and external factors and it will construct more robust underwater sensor networks over our proposed multiple path configuration scheme.

• 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.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39C no.2
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• pp.199-208
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• 2014

Code division multiple access (CDMA) is one of the promising medium access control (MAC) schemes for underwater acoustic sensor networks because of its robustness against frequency-selective fading and high frequency-reuse efficiency. As a way of performance evaluation, sea or lake experiment has been employed along with computer simulation.. In this study, we design the underwater CDMA forward-link transceiver and evaluate the feasibility aginst harsh underwater acoustic channel in water-tank first. Then, based on the water-tank experiment results, we improved the transceiver and showed the improvements in a lake experiment. A pseudo random noise code acquisition process is added for phase error correction before decoding the user data by means of a Walsh code in the receiver. Interleaving and convolutional channel coding scheme are also used for performance improvement. Experimental results show that the multiplexed data is recovered by means of demultiplexing at receivers with error-free in case of two users while with less than 15% bit error rate in case of three and four users.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.17 no.6
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• pp.1706-1727
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• 2023

Under Water Sensor Networks (UWSN) has gained attraction among various communities for its potential applications like acoustic monitoring, 3D mapping, tsunami detection, oil spill monitoring, and target tracking. Unlike terrestrial sensor networks, it performs an acoustic mode of communication to carry out collaborative tasks. Typically, surface sink nodes are deployed for aggregating acoustic phenomena collected from the underwater sensors through the multi-hop path. In this context, UWSN is constrained by factors such as lower bandwidth, high propagation delay, and limited battery power. Also, the vulnerabilities to compromise the aquatic environment are in growing numbers. The paper proposes an Energy-Efficient standalone Intrusion Detection System (EEIDS) to entail the acoustic environment against malicious attacks and improve the network lifetime. In EEIDS, attributes such as node ID, residual energy, and depth value are verified for forwarding the data packets in a secured path and stabilizing the nodes' energy levels. Initially, for each node, three agents are modeled to perform the assigned responsibilities. For instance, ID agent verifies the node's authentication of the node, EN agent checks for the residual energy of the node, and D agent substantiates the depth value of each node. Next, the classification of normal and malevolent nodes is performed by determining the score for each node. Furthermore, the proposed system utilizes the sheep-flock heredity algorithm to validate the input attributes using the optimized probability values stored in the training dataset. This assists in finding out the best-fit motes in the UWSN. Significantly, the proposed system detects and isolates the malicious nodes with tampered credentials and nodes with lower residual energy in minimal time. The parameters such as the time taken for malicious node detection, network lifetime, energy consumption, and delivery ratio are investigated using simulation tools. Comparison results show that the proposed EEIDS outperforms the existing acoustic security systems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.213-216
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• 2007

The paper deals with a approach to underwater acoustic based Ad-hoc communication, which allows major design strategies for Media Access Control (MAC) within a group of the autonomous underwater vehicles(AUV). The proposed MAC aims at deploying AUV-centric star topology, which minimizes overhead of sensor nodes and improves energy-efficiency. Furthermore, that is also well under long and unknown propagation delays of the underwater acoustic medium. The implemented MAC protocol makes it easier to achieve frame synchronization than TDMA due to deploying localized schedule time, in addition to saving energy consumption by letting nodes sleep. It is also superior to MACA and MACAW in terms of propagation delay. This scalable centralized protocol has the potential to serve as a primer for development of MAC protocol for future underwater acoustic based ad-hoc networks.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.405-411
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• 2011

As the interest in ocean environment monitoring and ocean development has been increased, the need for researches on underwater wireless sensor network (UWSN) and low power consuming acoustic modem for UWSN has been arisen. In this paper, we design and implement a micro-modem equipped with a tiny and omnidirectional transducer for underwater acoustic communications. In addition, we make experiments in a water tank and a pond in order to verify the performance of the developed modem in terms of supply voltage and communication distance, and analyze the results. According to the outdoor experiments, the modem can send data wirelessly in underwater at a distance of 40 meter with a data rate of 200 bps and a bit error rate of $10^{-5}$ when the supply voltage is 12 V. Due to its small size, low power consumption and omnidirectional property, it is expected that the modem which is implemented in this paper could be utilized for various applications based on UWSN.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.1
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• pp.135-141
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• 2016

Recently, the needs for the development and application of marine robots are increasing as marine accidents occur frequently. However, it is very difficult to acquire the information by utilizing marine robots in the marine environment. Therefore, the needs for the researches of sensor networks which are composed of underwater, surface and aerial robots are increasing in order to acquire the information effectively as the information from heterogeneous robots has less limitation in terms of coverage and connectivity. Although various researches of the sensor network which is based on marine robots have been executed, all of the underwater, surface and aerial robots have not yet been considered in the sensor network. To solve this problem, a collaborative control method based on the acoustic information and image by the sonars of the underwater robot, the acoustic information by the sonar of the surface robot and the optical image by the camera of the static-floating aerial robot is proposed. To verify the performance of the proposed method, the collaborative control of a MUR(Micro Underwater Robot) with an OAS(Obstacle Avoidance Sonar) and a SSS(Side Scan Sonar), a MSR(Micro Surface Robot) with an OAS and a BMAR(Balloon-based Micro Aerial Robot) with a camera are executed. The test results show the possibility of real applications and the need for additional studies.

• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.211-217
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• 2017

In this paper, we propose a bidirectional full duplex MAC (Medium Access Control) protocol for underwater acoustic networks. An underwater sensor node can set a back-off timer according to the priority of transmission. When the back-off timer expires, the underwater sensor node acquires a transmission opportunity. If a source node wants to send data to a destination node, it broadcasts RTS (Request-To-Send) including ID of the destination node to neighbor nodes. The destination node receiving RTS sends CTS (Clear-To-Send) to the source node to inform the bidirectional full duplex communication. After the source node receives CTS, the source node and the destination node can send the data to each other. In the underwater environment, the existing MAC protocol may take a lot of time for successful transmission of data due to long underwater propagation delay. On the other hand, the proposed bidirectional full duplex MAC protocol improves the throughput by shortening the time for successful transmission of data. In this paper, we analyze the throughput of the proposed bidirectional full duplex MAC protocol. In addition, we show that the proposed bidirectional full duplex MAC protocol has better performance in the presence of the long underwater propagation delay compared with existing MAC protocols for underwater environments.

• Journal of the Institute of Electronics and Information Engineers
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• v.50 no.1
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• pp.232-238
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• 2013

This paper study the position estimation of MBK system according to the non-linear filter for non-Gaussian noise in underwater sensor networks. In the filter to estimate location, recently, the extended Kalman filter (EKF) and particle filter are getting attention. EKF is widely used due to the best algorithm in the Gaussian noise environment, but has many restrictions on the usage in non-Gaussian noise environment such as in underwater. In this paper, we propose the improved One-Dimension Particle Filter (ODPF) using the distribution re-interpretation techniques based on the maximum likelihood. Through the simulation, we compared and analyzed the proposed particle filter with the EKF in non-Gaussian underwater sensor networks. In the case of both the sufficient statistical sample and the sufficient calculation capacity, we confirm that the ODPF's result shows more accurate localization than EKF's result.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.1
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• pp.33-40
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• 2011

In this paper, underwater acoustic communication experiment was carried out to test a performance of single carrier digital modulation schemes. The communication experiment was performed at real sea and tested modulation schemes are ASK, FSK with non-coherent detection and QPSK with coherent detection. A modulated image data was transmitted with data rates of 600bps~3Kbps. From the results of BER of the demodulated signal, ASK and FSK show the achievable BER of $10^{-3}{\sim}10^{-4}$ without compensation techniques and QPSK show that of $10^{-4}$ with linear equalizer.