• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2022.06a
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• pp.313-314
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• 2022

The intelligent maritime traffic information service provides a service to prevent collisions and stranding of ships based on the location information of ships periodically collected from ship equipment such as LTE-Maritime transceivers and AIS installed on ships. provided in real time. However, the above service may reduce the reliability of ship location information because GPS location information for measuring the ship's location may be cut off during transmission through LTE-Maritime or AIS networks, or phenomena such as location jumps and delays may occur. This study aims to estimate reliable position information to some extent even in an abnormal section through ship position prediction based on the existing received position information using the Kalman filter, which is an optimal estimation filter based on probability.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.5 s.347
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• pp.84-93
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• 2006

Ethernet-PON is an emerging access network technology that provides a low-cost method of deploying optical access lines between OLT and ONUs. It has a point-to-multipoint and multipoint-to-point architecture in downstream and upstream direction, respectively. Therefore, downstream packets are broadcast from an OLT toward all ONUs sithout collision. On the other hand, since alt ONUs share a common channel, the collision may be occurred for the upstream transmission. Therefore, earlier efforts on Ethernet-PON have been concentrated on an upstream MAC protocol to avoid collision. But it is needed to control downstream traffic in practical access network, where the network provider limits available bandwidth according to the number of users. In this paper, we propose a traffic control scheme for supporting the fairness of the downstream bandwidth. The objective of this algorithm is to guarantee the fairness of ONUs while maintaining good performance. In order to do this, we define the service probability that considers the past traffic information for downstream, the number of tokens and the relative size of negotiated bandwidth. We develop the simulation model for Ethernet-PON to evaluate the rate-limiting algorithm by using AWESIM. Some results are evaluated and analyzed in terms of defined fairness factor, delay and dropping rate under various scenario.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39A no.12
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• pp.708-717
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• 2014

In this paper, we present a secret key distribution protocol without resorting to a key management infrastructure targeting at providing a low-complexity distributed solution to wireless network. The proposed scheme extracts a secret key from the random fluctuation of wireless channels. By exploiting time division duplexing transmission, two legitimate users, Alice and Bob can have highly correlated channel gains due to channel reciprocity, and a pair of random bit sequences can be generated by quantizing the channel gains. We propose a novel adaptive quantization scheme that adjusts quantization thresholds according to channel variations and reduces the mismatch probability between generated bit sequences by Alice and Bob. BCH codes, as a low-complexity and pratical approach, are also employed to correct the mismatches between the pair of bit sequences and produce a secret key shared by Alice and Bob. To maximize the secret key extraction rate, the parameters, quantization levels and code rates of BCH codes are jointly optimized.

• Archives of design research
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• v.18 no.1 s.59
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• pp.49-58
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• 2005

Focusing on the information sender, message, channel, and receiver, the existing information theory deals with the noise, information contents, and probability of choice, which involve in the process of information transmission. In the current digital environment, besides simply conveying information itself through media, the important issue is how to efficiently convey information. Therefore, we need to analyze the theory in different perspective, and to research the Information redundancy for the methodology of information design. The redundancy causes the receiver to have attraction to the information and to reduce its contents due to its supplement and repetition. So it can play a role of efficient communication method. The concept of redundancy is applied to the communication of art such as literature, architecture, painting, and design to accomplish efficient communication. In order to get persuasive information design for the receiver's perspective we need to make use of this concept. The redundancy can be applied with the technical aspect of multimedia and Interaction, which add supplemental expression, or sort of event for the receiver's experience and memory. In the process of constructing information it can be applied with the structure of gaming redundancy, entropy, the accumulating communication code using entertaining feature, and storytelling methodology. The noise and entropy could be used for the means of making redundancy, not the obstacle to information. The redundancy gives the receiver attraction on the information and makes them have strong will of interpreting it so that the purpose of conveying information will be accomplished efficiently.

• The KIPS Transactions:PartC
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• v.13C no.2 s.105
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• pp.241-248
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• 2006

Mobile computing has such characteristics as portability, wireless network, mobility, etc. These characteristics cause various problems to mobile terminals like frequent disconnection, high error rate, and varying network status. These problems motivate us to develop an adaptive error control mechanism for supporting multimedia service in mobile computing environment. In this paper, we propose the Adaptive Error Control(AEC) scheme using client's buffer size and current error rate. After categorizing the status into four groups according to client's buffer size and current error rate, this scheme applies an appropriate error control scheme to each status. In this scheme, thresholds of buffer size and error rate are determined by the data transmission time, play rate and average VOP size, and by the probability of error for a sequence of packets. The performance of proposed scheme is evaluated by flaying MPEG-4 files on an experimental client/server environment, respectively. The results show that error correcting rate is similar to other schemes while the time for correcting error reduce a little. In addition, the size of data for correcting error is decreased by 23% compared with FEC and Hybrid FEC, respectively. Theses results demonstrate that the proposed scheme is more suitable in mobile computing environment with small bandwidth and varying environment than existing schemes.

• The KIPS Transactions:PartC
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• v.10C no.7
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• pp.943-954
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• 2003

The mobile telecommunication system has been growing exponentially after 1990s due to the high population in a city and the growth of mobile user. In this time, the current mobile system mainly concentrates on the voice communication. However, in the next generation, mobile users want to get very diverse services via mobile terminal such as the Internet access, web access, multimedia communication, and etc. For this reason, the next generation system, such as the UMTS (Universal Mobile Telecommunication Services) system, has to support the packet data service and it will play the major role in the system. By the way, since the Web service is based on TCP, most of the Internet traffic TCP traffic. Therefore, efficient transmission of TCP traffic will take very important role in the performance of packet data service. There are many researches about improving TCP performance over wireless network. In those schemes, the UMTS system adapts the link layer retransmission scheme. However, there are rarely studies about the exact performance of the link layer retransmission scheme in the face of dynamic changes of wireless environment over the UMTS system. The dynamic changes of wireless environment, such as wireless bandwidth, can degrade TCP performance directly. So, in this paper, we simulate and analyze the TCP performance in the UMTS system with dynamic wireless environments. Then, we propose a simple scheme for minimizing TCP performance degradation. As a result of simulation, we can find that when wireless environment is changed dynamically, the probability of TCP timeout is increased, and the TCP performance is degraded very much. In this situation, the proposed simple scheme shows good performance. It saves wireless resources and reduces the degradation of TCP performance without large overhead of the base station.

• Journal of IKEEE
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• v.7 no.2 s.13
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• pp.288-298
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• 2003

We consider a window-controlled selective-repeat ARQ scheme for error control between two adjacent nodes lying on a communication path. In this scheme, each packet to be transmitted is endowed with a serial number in a cyclic and sequential fashion. In turn, the transmitting node is not allowed to transmit a packet belonging to a window before every packet in the previous window is positively acknowledged. Such postponement of packet transmission incurs a degradation in throughput and delay performance. In this paper, aiming at improving packet delay performance, we employs a supplement scheme in which a serial number is duplicated within a frame. Classifying duplication rules into fixed, random and adaptive categories, we present candidate rules in each category and evaluate the packet delay performance induced by each duplication rule. From numerical examples, we observe that duplicating serial numbers, especially ADR-T2 effectively reduces mean packet delay for the forward channel characterized by a low packet error rate. We also reveal that such delay enhancement is achieved by a high probability of hitting local optimal window size.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.96-107
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• 2015

VANET technologies provide real-time traffic information for mitigating traffic jam and preventing traffic accidents, as well as in-vehicle infotainment service through Telematics/Intelligent Transportation System (ITS). Due to the rapid increasement of various requirements, the vehicle communication with a limited resource and the fixed frame architecture of the conventional techniques is limited to provide an efficient communication service. Therefore, a new flexible operation depending on the surrounding situation information is required that needs an adaptive design of the network architecture and protocol for efficiently predicting, distributing and sharing the context-aware information. In this paper, Vehicle-to-Infrastructure (V2I) based on communication between vehicle and a Road Side Units (RSU) and Vehicle-to-Vehicle (V2V) based on communication between vehicles are effectively combined in a new MAC architecture and V2I and V2V vehicles collaborate in management. As a result, many vehicles and RSU can use more efficiently the resource and send data rapidly. The simulation results show that the proposed method can achieve high resource utilization in accordance. Also we can find out the optimal transmission relay time and 2nd relay vehicle selection probability value to spread out V2V/V2I collaborative schedule message rapidly.

• Journal of KIISE:Information Networking
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• v.29 no.4
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• pp.447-458
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• 2002

In this paper, we design and implement Wireless Transaction Protocol(WTP) and evaluate it for wireless transaction processing in mobile computing environments. The design and implementation of WTP are based on the coroutine model that might be suitable for light-weight portable devices. We test the compatibility between our product and the other products such as Nokia, Kannel and WinWAP For the evaluation of WTP, we use an Internet simulator that can arbitrary generate random wireless errors based on the Gilbert model. In our experiment, the performance of WTP is measured and compared to those of Transmission Control Protocol(TCP) and TCP for Transactions. The experiment shows that WTP outperforms the other two protocols for wireless transaction processing in terms of throughput and delay. Especially, WTP shows much higher performance In ease of high error rate and high probability of burst errors. This comes from the fact that WTP uses a small number of packets to process a transaction compared to the other two protocols and introduces a fixed time interval for retransmission instead of the exponential backoff algorithm. The experiment also shows that the WTP performance is optimized when the retransmission counter is set to 5 or 6 in case of high burst error rate.

• Journal of the Korean Society of Radiology
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• v.4 no.1
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• pp.11-17
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• 2010

A urolithiasis, also called calculus, is one of the brutal illnesses, which has constantly harassed humanbeings from time immemorial. However, there is no appropriate method of prevention so far. So, Urological therapy must be followed upon those patients. The biggest problem of urolithiasis is usually causing harsh pain, fever, and throw up. The pain would be more intensified when something came through the ureter or the moment of convulsion caused beyond transmission of urinary calculus. Even strong painkillers, such as fentanyl and Pethidine, can not handle those harshly pain easily. Therefore, a prompt action of medical check up and its therapy must be required to those patients. This thesis paper has put the accent on the specific therapy, known as ESWL (Extracorpereal Shock Wave Lithotripsy), which have generated quite optimum resolution to patients, who received harsh pain from Proximal ureteral stone and Mid ureteral stone and because of its low provability of pulverization. The results of the experiment confirmed that the stone, located between Proximal and Mid ureter, has lower provability of pulverization than distal ureter, because its accuracy rate on shock wave, in respect of breathing, are low. However, decrease in discharge interval have enhanced provability of pulverization. it can also intensify probability of pulverization and its safety by discharging high power with appropriate intervals, and that is more efficient than discharging low power with frequent time.