• Journal of the Korean Institute of Intelligent Systems
• /
• v.23 no.5
• /
• pp.418-422
• /
• 2013

This paper has considered the location estimation problem in two dimension space by using a non-linear filter under non-Gaussian noise in underwater acoustic sensor networks(UASNs). Recently, the extended Kalman filter (EKF) is widely used in location estimation. However, the EKF has a lot of problems in the non-linear system under the non-gaussian noise environment like underwater environment. In this paper, we propose the improved Two-Dimension Particle Filter (TDPF) using the re-interpretation distribution techniques based on the maximum likelihood (ML). Through the simulation, we compared and analyzed the proposed TDPF with the EKF under the non-Gaussian underwater sensor networks. Finally, we determined that the TDPF's result shows more accurate localization than EKF's result.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.34 no.10B
• /
• pp.955-963
• /
• 2009

In this paper, we propose a medium access control(MAC) protocol for reducing the energy efficiency and for improving the transmission efficiency in underwater acoustic sensor networks. In underwater environment, the transmission delay is longer and bandwidth is smaller than terrestrial environment. Considering these points, we propose a new MAC protocol to enhance throughput and to manage efficiently the energy of nodes. The proposed protocol operates as a channel reservation scheme to decrease data collisions, and uses a mechanism to control the hidden node problem and the exposed node problem occurred in ad hoc networks. The proposed protocol consists of the slotted based transmission frame and reduces data collisions between nodes by putting separately the reservation period in the transmission frame. In addition, it is able to solve the hidden node problem and the exposed node problem by reservation information between nodes. We carry out the simulation to evaluate the proposed protocol in terms of the average energy consumption, the ratio of collision, throughput, and the average transmission delay, and compare the proposed protocol to a traditional MAC protocol in the underwater environment. The simulation results show that the proposed protocol outperforms the traditional protocol under a various of network parameters.

• The Journal of the Acoustical Society of Korea
• /
• v.32 no.1
• /
• pp.86-94
• /
• 2013

In this paper, we propose a network coding scheme that is one of the most promising techniques for overcoming transmission errors in underwater acoustic communications. It is assumed that the proposed scheme operates in a Code Division Multiple Access (CDMA) network where multiple sensor nodes share the underwater acoustic channel in both the frequency and the time domains by means of orthogonal codes. The network topology deploys multi-hop transmission with relaying between multiple source nodes and one destination node via multiple relay nodes. The proposed scheme is evaluated in terms of the successful packet delivery ratio of end-to-end transactions under varying packet loss rates. A computer simulation shows that the successful delivery ratio is maintained at over 95% even when the packet loss rate reaches 50%.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2007.06a
• /
• pp.213-216
• /
• 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
• /
• v.40 no.5
• /
• pp.809-811
• /
• 2015

In this paper, for the purpose of providing high data rate services, the multi-hop frame structure is designed for the underwater acoustic (UWA) short-range system which is proposed as a part of ocean surveillance and tracking network (OSTN). Under the measured underwater channel environment, the link-level system performance are also evaluated. Simulation results show not only the packet error rate (PER) comparisons, but the optimal modulation and coding scheme (MCS) levels for the orthogonal frequency division multiplexing (OFDM) based short-range UWA communications network.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.3 no.2
• /
• pp.389-396
• /
• 1999

In this paper, we propose a multiple underwater object classification and tracking algorithm using the narrowband tonal and frequency line features extracted from the frequency spectrum of the acoustic signal. The general algorithm using the wideband and narrowband energy has a high tracking error when objects are close and cross each other. But the proposed algorithm shows a good tracking performance for the simulation scenarios generated by the real acoustic data.

• Journal of Institute of Control, Robotics and Systems
• /
• v.15 no.6
• /
• pp.641-648
• /
• 2009

Currently several kinds of sensor localization methods have been developed for terrestrial wireless sensor networks. This study, in order to extend the field to underwater environments, a localization technique is studied for UWSNs (Underwater Wireless Sensor Networks). In underwater environments, RF (Radio Frequency) signal is not suitable for underwater usage because of extremely limited propagation. Because of that reason UWSNs should be constituted with acoustic modems. But, to realize underwater application, we can borrow many design principles from ongoing research for terrestrial environments. So, in this paper we introduce the modified localization algorithm using ToA method which is based on the terrestrial research. First of all, we study the localization techniques for terrestrial environments where we investigate possible methods to underwater environment. And then the appropriate algorithm is presented in the underwater usage. Finally the proposed underwater based localization algorithm is evaluated by using computer.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.48 no.6
• /
• pp.97-108
• /
• 2011

Systems for underwater environment monitoring and natural resources can be considered as a part of digital convergence where real-time data transmission is possible with the help of underwater wireless sensor network (UWSN). One of key technologies required for the deployment of the systems is underwater acoustic micro modem. In this work, we design and implement an acoustic modem equipped with a commercial omnidirectional transducer. We also make experiments at the northern Han river for the verification of the developed modem. According to the experiments, the modem supports the working distance of 250 m and the data rate of 200 bps with a negligible bit error rate. It is expected that the acoustic modem can be used for various applications based on UWSN in a near future.

• The Journal of the Acoustical Society of Korea
• /
• v.36 no.1
• /
• pp.39-48
• /
• 2017

CDMA (Code Division Multiple Access) is promising medium access control schemes for underwater acoustic sensor networks because of its robustness against frequency-selective fading and high frequency-reuse efficiency. In this paper, we design diversity schemes of underwater CDMA transceiver for the forward and reverse links. User data are multiplexed by Walsh code and a pseudo random noise code acquisition process is added for phase error correction before decoding the user data at the receiver. Then, the diversity reception using equal gain combining and maximal ratio combining is performed in order to minimize performance degradation caused by rich multipath fading of underwater acoustic channel. We evaluated the performance of diversity transceiver through lake experiment, which was performed at Lake Kyungcheon, Mungyeong city using two transmitters and two receivers placed 460 m apart at an average depth of 40 m. The lake experiment results show that user data are recovered with error-free in both of the forward and reverse links.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.6
• /
• pp.1-10
• /
• 2021

The interest in underwater acoustic sensor networks (UWASNs), along with the rapid development of underwater industries, has increased. To operate UWASNs efficiently, it is important to adopt well-designed medium access control (MAC) protocols that prevent collisions and allow the sharing of resources between nodes efficiently. On the other hand, underwater channels suffer from a narrow bandwidth, long propagation delay, and low data rate, so existing terrestrial node pairing schemes for non orthogonal multiple access (NOMA) cannot be applied directly to underwater environments. Therefore, a multi-dimensional node pairing scheme is proposed to consider the unique underwater channel in UWASNs. Conventional NOMA schemes have considered the channel quality only in node pairing. Unlike previous schemes, the proposed scheme considers the channel gain and many other features, such as node fairness, traffic load, and the age of data packets to find the best node-pair. In addition, the sender employs a list of candidates for node-pairs rather than path loss to reduce the computational complexity. The simulation results showed that the proposed scheme outperforms the conventional scheme by considering the fairness factor with 23.8% increases in throughput, 28% decreases in latency, and 5.7% improvements in fairness at best.