• The Journal of the Acoustical Society of Korea
• /
• v.34 no.6
• /
• pp.463-469
• /
• 2015

In this paper, we propose an underwater propagation delay-aware medium access control protocol and evaluate the performance of the proposed protocol. In the proposed propagation delay-aware medium access control protocol, a sink node can restore the received RTS frames that are not piled up in a slot time. We analyze and compare the performance of the proposed underwater propagation delay-aware medium access control protocol with that of the conventional medium access control protocol in various environments.

• Journal of KIISE:Information Networking
• /
• v.35 no.1
• /
• pp.1-10
• /
• 2008

Once the sensor node in wireless sensor networks is installed, it usually operates without human intervention for a long time. The remote code update scheme is required because it is difficult to recall the sensor node in many situations. Therefore, studies on the reliable and efficient transport protocol for code propagation in wireless sensor networks have been increasingly done. However, by considering only the stability aspect of transmission, most of previous works ignore the consideration on the fast code propagation. This results the energy inefficiency by consuming unnecessary energy due to the slow code propagation. In this paper, in order to overcome limitation of the previous code propagation protocols, we propose a new code propagation protocol called "FCPP(Fast Code Propagation Protocol)". The FCPP aims at improving the reliability at well as performance. For this purpose, the FCPP accomplishes the fast code propagation by using the RTT-based transmission rate control and NACK suppression scheme, which provides a better the network utilization and avoids a unnecessary transmission delay. Based on the ns-2 simulation result, we prove that the FCPP Improves significantly both reliability and performance.

• Journal of the Institute of Electronics Engineers of Korea SP
• /
• v.46 no.1
• /
• pp.63-70
• /
• 2009

The purpose of this paper is to propose a CSMA/CA protocol to reduce the delay time and increase the throughput of the original CSMA/CA protocol. In underwater environments, the efficiency of the protocol is reduced due to the increase of the propagation delay time, which results in increase of the collision possibility causing lowering of the transmission efficiency Considering this propagation delay, this paper propose to insert the STANDBY frame in a CTS packet in order to avoid the TimeOut status of the CSMA/CA protocol. According to the simulated test results, proposed protocol is increased about 20% throughput than original CSMA/CA protocol. And the more value of propagation per transmission delay 'a' is low, the more throughput of protocol is better.

• Journal of the Korean Institute of Telematics and Electronics A
• /
• v.33A no.2
• /
• pp.50-58
• /
• 1996

This paper proposes the channel-access protocol suitable to a very high speed photonic WDM network with star configuration, which can provide a high channel utilization and insensitivity to the propagation delay. The proposed protocol employs a control channel and a simple status table to deal with the propagation delay which has been a major limiting factor in the performance of the very high speed optical communication networks. The control channel transmits control information in order to reserve access on data channels, and each node constitutes a status table after the reception of control pckets which holds information about the availbility of destination node and data channel. The proposed protocol is insensitive to the propagation delay time by removing necessity of the retransmission and by allowing parallel transmission of control packet and data packets. It is proved in analysis and discrete event simulation that the proposed protocol is superior in throughput and mean delay, especially at the high load conditions compared to the existing high speed channel-access protocols.

• Journal of the Institute of Convergence Signal Processing
• /
• v.12 no.1
• /
• pp.44-49
• /
• 2011

The need of data transmission in oceans and other underwater mediums are increasing day by day, so as the research. The underwater medium is very different from that of air. Propagation of electromagnetic wave in water or underground is very difficult because of the conductivity of the propagation materials. In this case, we usually use acoustic signals as ultrasonic but, they are not easy to transfer long distance with coherent method because of time varying multipaths, Doppler effects and attenuations. So, we use non-coherent methods such as FSK or ASK to communicate between long distances. But, as the propagation speed of acoustic wave is very slow, BW of the channel is narrow. It is very hard to guaranty the enough speed for the transmission of digital image data. In previous studies, we proposed this data communication protocol theoretically. In this paper, an underwater channel is modeled and this protocol is tested in this channel condition. The results show that the protocol is 4-6 times faster than ASK. Some relations and results are shown depending on the data length, channel length, bit rate etc.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.1 no.1
• /
• pp.105-111
• /
• 1997

This Paper Proposes a new efficient system design strategies for the acoustic-based underwater multiple modem and media access control protocol. The system aims to establish the acoustic-based communication network of an underwater vehicles for deep sea mining, which ensures a certain level of maximum throughput regardless of the propagation delay of acoustic and allows fast data transmission through the acoustic-based multiple channel. A media access control protocol for integrated communication network and it's acoustic-based communication modems that allows 'peer-to-peer' communication between a surface mining plant multiple underwater system is designed, and the proposed media access control protocol is implemented for its verification. Furthermore, a proposed design strategies which make it possible to control the multiple vehicle for an underwater mining is presented in this paper.

• Journal of Ocean Engineering and Technology
• /
• v.11 no.4
• /
• pp.180-188
• /
• 1997

This paper proposes a new efficient MAC(Media Access Control) protocol to establish the ultrasonic communication network for underwater vehicles, which ensures a certain level of maximum throughput regardless of the propagation delay of ultrasonic and allows fast data transmission through the multiple ultrasonic communication channel. A MAC protocol for underwater communication network that allows 'peer-to-peer' communication between a surface ship and multiple underwater systems is designed, and the proposed control protocol is implemented for its verification.

• Journal of the Institute of Convergence Signal Processing
• /
• v.10 no.1
• /
• pp.1-6
• /
• 2009

Propagation of electromagnetic wave in the water or underground is very difficult because of the conductivity of the propagation materials. In this case, we usually use acoustic signal as ultrasonic but, it is not easy to transfer long distance with coherent method because of time varying multipath, doppler effect, and attenuations. So, we use noncoherent method as FSK to communicate between long distances. But, as the propagation speed of acoustic sound is very slow, the BW of the channel is narrow. It is very hard to guaranty the enough speed of communication like digital image data. In this paper, we proposed a new data communication protocol which can transmit multi-bit digital data with every single ping, and improve the data communication speed in the water.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2017.05a
• /
• pp.621-624
• /
• 2017

In this paper, we propose a protocol synchronizing to packet trains in a underwater acoustic networks with limitations such as long propagation delay, low data rate, high packet loss. The proposed protocol employs an one-way communication scheme to calculate packet arrival time differences of consecutively transferred packets and minimizes uncertain variation effect of long propagation delay. Simulation results shows the superiority of our protocol, compared with a previously proposed one under the given network conditions.

• Plant Biotechnology Reports
• /
• v.2 no.3
• /
• pp.213-218
• /
• 2008

Swertia chirata is an endangered gentian species that prefers to grow at higher altitudes. This ethnomedicinal herb is known primarily for its bitter taste caused by the presence of important phytochemicals that are directly associated with human health benefits. Due to a continuous loss of habitat and inherent problems of seed viability and seed germination, alternative strategies for propagation and conservation are urgently required to prevent the possible extinction of this species. We have formulated a reproducible protocol for the rapid propagation and conservation of this plant using leaves taken from in vitro shoot cultures. Direct induction of more than seven shoot buds per explant was achieved for the first time when the explants were placed on MS medium supplemented with $2.22{\mu}M$ N-6-benzyladenine, $11.6{\mu}M$ kinetin, and $0.5{\mu}M$ ${\alpha}-naphthalene$ acetic acid. Direct organogenesis was noted exclusively from the adaxial surface of the basal segments of leaves. Leaves closer to the apical meristem were more responsive than those farther away from the meristem. Plants raised through direct organogenesis were evaluated for their clonal fidelity by chromosomal analysis and DNA fingerprinting. Complete plants were successfully transferred to the field condition and produced viable seeds. Given the enormous potential of this age-old medicinal plant in terms of potential health-benefitting drugs, this protocol can be used for commercial propagation purposes and to initiate future genetic improvement studies.