• The Journal of the Acoustical Society of Korea
• /
• v.40 no.3
• /
• pp.183-191
• /
• 2021

A time-series variation of temperature, salinity, and underwater sound speed was analyzed using an Array for Real-time Geostrophic Oceanography (ARGO) float which autonomously collects temperature and salinity for about 10month with 2 days cycle among 12 floats in the center of the Yellow Sea. As a result, the underwater sound channel appeared below the thermocline as the surface sound channel, which is dominant in the winter season, reduced in April. Besides, for a certain time in the spring season, the sound ray reflected the sea surface frequently due to the short-term temperature inversion effect. Based on the case of successful observation of ARGO float in the shallow water, using prolonged monitoring unmanned platform may contribute to predicting sound transmission loss if the temperature inversion and sound channel including background environment focusing are investigated in the center of the Yellow Sea.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.18 no.5
• /
• pp.1390-1411
• /
• 2024

Underwater Wireless Sensors Networks (UWSNs) are deployed in remotely monitored environment such as water level monitoring, ocean current identification, oil detection, habitat monitoring and numerous military applications. Providing scalable and efficient routing is very challenging in UWSNs due to the harsh underwater environment. The biggest difficulties are the nodes inherent movement due to water current, long delay in data transmission, low bandwidth of the acoustic signal, high error rate and energy scarcity in battery powered nodes. Many routing protocols have been proposed to solve the aforementioned problems. There are three broad categories of routing protocols namely depth based, energy based and vector-based routing. Vector Based Forwarding protocols perform routing through virtual pipeline by defining their radius which give proper direction to packets communication. We proposed a routing protocol termed as Path-Oriented Energy Scaled Expanded Vector Based Forwarding (PESEVBF). PESEVBF takes into account all parameters; holding time, the source nodes packets routing path and void holes creation on the second hop; PESEVBF not only considers the packet upward advancement but also focus on density of the forwarded nodes in terms of number of potential forwarding and suppressed nodes for path selection. Node selection in resultant holding time is based on minimum Path Factor (PF) value. Moreover, the suppressed node will be selected for packet forwarding to avoid the void holes occurrences on the second hop. Performance of PESEVBF is compared with other routing protocols using matrices such as energy consumption, packet delivery ratio, packets dropping ratio and duplicate packets creation indicating considerable performance improvement.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.1
• /
• pp.660-665
• /
• 2018

Research into underwater wireless networks that enable the monitoring and controlling of the ocean environments has been continuing for disaster prevention and military proposes, as well as for the exploitation of ocean resources throughout the world. A research group led by Hoseo university has been studying a distributed underwater monitoring and controlling network. In this study, we developed an interpolator for acoustic communication between an underwater base station controller and underwater base station, which is included in this network. The underwater acoustic communication provided by this network defines four links whose sampling rates are different. Low power consumption is one of the most important requirements. Therefore, we adopted CIC interpolators, which are known to act as filters with a low power consumption, and some CIC interpolators with an appropriate changing rate were selected depending on the link. However, these interpolators have a large passband drop and wide transition region. To solve these problems, we added a compensator and half-band filter. After verifying the algorithm by using Matlab, we designed and verified it with Verilog-HDL in a ModelSim environment.

• IEMEK Journal of Embedded Systems and Applications
• /
• v.9 no.3
• /
• pp.165-171
• /
• 2014

In this paper, we propose the hardware and software of a test-bed of a hovering AUV (autonomous underwater vehicle). Test-bed to develop as the underwater robot for the hovering -type is planning to apply for marine resource development and exploration for deep sea. The RTU that controls a azimuth thruster and a vertical thruster of test-bed is a intergrated-type thruster. The main control unit that collects sensor's data and performs high-speed processing and controls a movement of test-bed is a underwater hybrid navigation system. Also it transfers position, posture, state information of test-bed to the host PC of user using a wireless communication. The host PC checks a test-bed in real time by using a realtime monitoring system that is implemented by LabVIEW.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.29 no.2
• /
• pp.109-116
• /
• 1993

Underwater acoustic positioning systems have been extensively used not only in surface position fixing but also in underwater position fixing. Recently, these systems have been applied in the field of installation and underwater inspection of offshore platforms etc. But in these systems are included the fixing errors as results of a signal with additive noise and irregular motion of vessel by ocean waves. To improve the accuracy of the position fixing a Kalman filter is applied to the supershort baseline (SSBL) acoustic positioning system with beacon mode in noise conditions. The position data obtained by the Kalman filter is compared with raw position data and it is confirmed in the simulation that the former is more accurate than the latter. And an indicator monitoring the filtering effect is described while ship's moving.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.5
• /
• pp.372-378
• /
• 2016

A mound was constructed to install a caisson and sofa blocks underwater. The mound riprap, which were of uniform grade, size, shape, and specific gravity, formed the foundation for the support superstructure. Also, rubble leveling works were performed before installing structures such as caissons. In this study, underwater construction equipment was developed with a remotely controlled operating system and underwater environment monitoring system for unmanned underwater rubble leveling work. The performance of the developed equipment was verified using on-land and underwater tests. In addition to the performance verification, the construction process and economic efficiency of the equipment should be checked before applying it to the real construction field for commercial purposes. In this paper, a construction process using the developed equipment was proposed and compared with the existing rubble leveling method. The results demonstrated that the new construction method has higher economic efficiency and safety than the existing construction method.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.24 no.3
• /
• pp.405-411
• /
• 2020

Recently, studies on underwater communication, related to the development of underwater resources, disaster monitoring and defense, have been actively carried out. In the design of wireless communication systems, path loss is the most important information to derive a link budget that is required to guarantee communication reliability by calculating received power level for the given communication link. The underwater acoustic channel have different characteristics according to geographical location and relevant environmental factors such as water temperature, depth, wave height, algae, and turbidity. Subsequently, many research institutes aiming to develop underwater acoustic communication systems are researching actively on the underwater acoustic channels in various sea areas. In Korea, however, studies on the path loss of the acoustic channel are still insufficient. Therefore, in this study, the path loss of the acoustic channel are studied based on measurement data of the at-sea experiment conducted at Geohae-do, southern sea of Korea.

• Journal of the Institute of Convergence Signal Processing
• /
• v.23 no.2
• /
• pp.50-61
• /
• 2022

This work demonstrates the design and evaluation of Aqua-Aware, a lightweight miniaturized light emitting diode (LED) based underwater compact sensor node which is used to obtain different characteristics of the underwater environment. Two optical sensor nodes have been designed, developed, and evaluated for a short and medium link range called as Aqua-Aware short range (AASR) and Aqua-Aware medium range (AAMR), respectively. The hardware and software implementation of proposed sensor node, algorithms, and trade-offs have been discussed in this paper. The underwater environment is emulated by introducing different turbulence effects such as air bubbles, waves and turbidity in a 4-m water tank. In clear water, the Aqua-Aware achieved a data rate of 0.2 Mbps at communication link up to 2-m. The Aqua-Aware was able to achieve 0.2 Mbps in a turbid water of 64 NTU in the presence of moderate water waves and air bubbles within the communication link range of 1.7-m. We have evaluated the luminous intensity, packet success rate and bit error rate performance of the proposed system obtained by varying the various medium characteristics.

• Journal of Korea Multimedia Society
• /
• v.14 no.2
• /
• pp.258-268
• /
• 2011

Underwater acoustic sensor networks can be used disaster prevention and environmental monitoring systems in underwater environments. Because, the underwater environment is different from the ground, the long propagation delay, low transfer rates and limited bandwidth characteristics should be considered. In this, paper will propose the MAC protocol that allocates time slot into each node according to priority policy through the period of contention-free slot reservation in underwater acoustic sensor networks in order to avoid collision and minimize energy consumption waste. We perform mathematical analysis to evaluate the performance of the proposed protocol with regard to the collision probability, the energy consumption by collision, throughput and channel utilization. We compare the proposed protocol with the conventional protocol, and the performance results show that the proposed protocol outperforms the conventional protocol.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.39B no.6
• /
• pp.360-369
• /
• 2014

Underwater Acoustic Sensor Networks(UASN) enables varied study from collected data of underwater environments such as pollution monitoring, disaster prevention. The collected data is transmitted from underwater to terrestrial communication entity by acoustic communication. Because of the constraints of underwater environments include low data rate and propagation delay, it is difficult to apply cryptographic techniques of terrestrial wireless communication to UASN. For this reason, if the cryptographic techniques are excluded, then collected data will be exposed to security threats, such as extortion and forgery, during transmission of data. So, the cryptographic techniques, such as the authentication and key establishment protocol which can confirm reliability of communication entities and help them share secret key for encryption of data, must need for protecting transmitted data against security threats. Thus, in this paper, we propose the light weight authentication and key establishment protocol.