• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.4
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• pp.76-89
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• 2014

In this paper, we propose a MAC(Media Access Control) protocol based on flexible RWT(RTS Waiting Time) for underwater mobile ad-hoc networks with a three-way handshaking mechanism. This protocol can solve a problem of collision between RTS(Request-To-Send) and CTS(Clear-To-Send) packets in existing MACA(Multiple Access with Collision Avoidance) protocol. This proposed MAC protocol is also an effective protocol which can apply to underwater mobile ad-hoc networks in a real field by using implementable technologies. We set flexible RTS Waiting Time called RWT, considering various characteristics of underwater environment. It is possible to support variable network size according to node mobility. Finally, we conduct a performance evaluation between proposed MAC protocol and existing MACA based MAC protocol through practical implementation and experiment. As a result, we verify the superiority of our proposed MAC protocol in terms of throughput, packet drop rate, average transmission time, energy consumption and channel utilization.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.995-1001
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• 2005

Implicit Integration has become a standard approach to efficient cloth animation, and it guarantees the stability of the system so that large steps can be used. Therefore, it is regarded as the best method for the real-time or interactive animation of cloth. Since the implicit method was introduced for stable cloth animation, various cloth animation techniques based on the method have been proposed. It is now possible to generate the real-time animation of cloth model with thousands of mass-point in general PC environments. Although the implicit method guarantees the stability, the implementation of the implicit method is generally more difficult than that of the explicit method. Even worse, it is very difficult to parallelize the computation process of the implicit method. The cloth animation with implicit method can be formalized as a linear system solving. In this paper we propose an stable and efficient cloth animation techniques based on the implicit method. The proposed method can be easily parallelized. Self-collision is another important issue in cloth animation, we also propose an efficient self-collision avoidance techniques.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.745-748
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• 2001

Digital-ship is the next-generation ship with an one-man bridge system which consists of INS(Intelligent Navigation System), AIS(Automatic Identification System), and IMIT(Integrated Maritime Information Technology). INS implements the functions is related of the ship's navigation, and supports in the digital GIS environments optimal route planning, stranding and a collision avoidance among the ship, an economic navigation, and an integrated control of ship's engine. AIS prevents the ship's collision by means of transmitting periodically the own ship's information to the other ship or the shore control center. IMIT systems supports the integrated fiat-form in ships, the communication between a ship and a control center of the land using the INMARSAT, OrbComm, Ocean Observation Satellite, and etc. The satellite communication in ships can monitor the ship at an earth control renter. This paper deals with the method for system implementation of digital-ship and the detailed sub-system.

• Journal of Advanced Navigation Technology
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• v.27 no.5
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• pp.552-560
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• 2023

Aircraft midair collisions are dangerous events that can cause massive casualties. To prevent this, civil aviation has mandated the installation of TCAS (ACAS), which is becoming more sophisticated with the help of new technologies. However, there are institutional problems in collecting data for TCAS research in Korea, limiting the ability to obtain data for personal research. ADS-B and Mode-S automatic broadcast various information about the flight status of the aircraft. This data also contains information about TCAS RA, which can be used by anyone to find examples of TCAS RA operation. We used the databases of ADS-B Exchange and Opensky-Network to acquire data and visually represent three TCAS RA cases through Python coding. We also identified domestic TCAS cases in the first half of 2023 and analyzed their characteristics to confirm the usefulness of the data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.3B
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• pp.165-173
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• 2012

In this paper, we propose a random backoff scheme for Emergency Warning Messages (EWMs) in the vehicle-to-vehicle environment. The EWMs are disseminated from a vehicle that detects an emergency situation to other vehicles in a multi-hop fashion. Since the vehicle-to-vehicle communication based on IEEE 802.11 adapts CSMA/CA, the density of vehicles increase the probability of collisions between transmissions. Moreover, in the presence of background traffic, the EWM should have a higher priority than that of other messages in neighboring vehicles. To that end, we propose the Distant-Dependent Adaptive Backoff (DDAB) scheme, which set a different contention window for random backoff depending on the distance from the sender to the receiver. In the case when a vehicle is expected to located in the outskirts of the communication boundary, the proposed scheme makes the contention window size small in order to compete the background traffic transmission. Otherwise the contention window is set to a large number to reduce the collision possibility among the EWM transmissions. Via simulations, we show that the proposed scheme performs better than the previous schemes for EWM.

• Journal of Advanced Navigation Technology
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• v.8 no.1
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• pp.65-72
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• 2004

A basic access method using for IEEE 802.11a wireless LANs is the DCF method that is based on the CSMA/CA. But, Since IEEE 802.11 MAC layer uses original backoff algorithm (Exponential backoff method), when collision occurs, the size of contention windows increases the double size. Hence, packet transmission delay time increases and efficiency is decreased by original backoff scheme. In this paper, we have analyzed TCP packet transmission time of IEEE 802.11 MAC DCF protocol for wireless LANs using a proposed enhanced backoff algorithm. From the results, in OFDM/quadrature phase shift keying channel (QPSK), we can achieve that the transmission time in wireless channel decreases as the TCP packet size increases and based on the data collected, we can infer the correlation between TCP packet size and total message transmission time, allowing for an inference of the optimal packet size in the TCP layer.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.11
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• pp.12-19
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• 2015

In network-centric warfare, the communication network has played a significant role in defeating an enemy. Especially, the urgent and important data should be preferentially delivered in time. Thus, we proposed a priority MAC protocol based on CSMA/CA with Binary Exponential Back-off for tactical wireless networks. This MAC protocol suggested a PCW(Prioritized Contention Window) with differentiated back-off time by priority and a RBR(Repetitive Back-off Reset) to reset the remaining back-off time. The results showed that this proposed MAC has higher performance than those of DCF(Distributed Coordination Function) in the transmission success rate and the number of control packet transmission by reducing the packet collision. Thus, it produced more effective power consumption. In comparison with DCF, this proposed protocol is more suitable in high-traffic network.

• Journal of the Korean Institute of Intelligent Systems
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• v.13 no.1
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• pp.51-56
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• 2003

The main goal of existing mobile robot system was a complete autonomous navigation and the vision information was just used as an assistant way such as monitoring For this reason, the researches have been going towards sophistication of autonomousness gradually and the production costs also has been risen. However, it is also important to control remotely an inexpensive mobile robot system which has no intelligence at all. Such systems may be much more effective than fully autonomous systems in practice. Visual information from a simple camera and distance information from ultrasonic sensors are used for this system. Collision avoidance becomes the most important problem for this system. In this paper, we developed a force feedback joystick to control the robot system remotely with collision avoiding capability. Fuzzy logic is used for the algorithm in order to implement the expert s knowledge intelligently. Some experimental results show the force feedback joystick werks very well.

• Journal of Korean Society of Transportation
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• v.27 no.6
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• pp.109-118
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• 2009

The conventional lane changing model has been developed without acceleration or deceleration of vehicles at target lane. Thus, existing lane changing models have limitation to apply in real world. In this paper, lane changing model considered acceleration or deceleration, and calculated the safety distance between subject vehicle and adjacent vehicles for lane changing as well. Simulation was conducted to verify the validity and the efficiency of the developed lane changing model in this paper. Several scenarios were carefully examined by safety distance between subject vehicle and adjacent vehicles. In the result, it was verified that if gap between subject vehicle and adjacent vehicles is larger than safety distance, lane changing behavior between subject vehicle and adjacent vehicles avoids collision. The suggested lane changing model may be applied at the future driver assistance system and advanced safety vehicle.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.391-398
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• 2011

In this paper, we propose a MAC protocol for visible light wireless LAN using LED light. The proposed MAC protocol has a function of automatic direction optimization for LED transceiver. There is periodical time slot for broadcasting and registration in the proposed MAC protocol. We used polling method for data transfer in the protocol since visible light is hard to detect carrier and collision by other mobile stations; thus we cannot use CSMA/CD method in visible light LAN. We also amended the MAC frame of IEEE 802.11 to propose a revised version for visible light wireless LAN using LED light. We investigate the performance of the proposed MAC protocol. When the bit rate of physical layer is 100 Mb/s, the net data throughput using the proposed MAC protocol is estimated to 94.386 Mb/s.