• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.38B no.7
• /
• pp.543-552
• /
• 2013

For the safety messages in IEEE 802.11p/WAVE vehicles network environment, strict periodic beacon broadcasting requires status advertisement to assist the driver for safety. In crowded networks where beacon message are broadcasted at a high number of frequencies by many vehicles, which used for beacon sending, will be congested by the wireless medium due to the contention-window based IEEE 802.11p MAC. To resolve the congestion, we consider a MAC scheme based on slotted p-persistent CSMA as a simple non-cooperative Bayesian game which involves payoffs reflecting the attempt probability. Then, we derive Bayesian Nash Equilibrium (BNE) in a closed form. Using the BNE, we propose new congestion control algorithm to improve the performance of the beacon rate under saturation condition in IEEE 802.11p/WAVE vehicular networks. This algorithm explicitly computes packet delivery probability as a function of contention window (CW) size and number of vehicles. The proposed algorithm is validated against numerical simulation results to demonstrate its stability.

• Journal of Korea Multimedia Society
• /
• v.19 no.2
• /
• pp.155-162
• /
• 2016

Several distributed scheduling policies have been proposed with the objective of attaining the maximum throughput region or a guaranteed fraction throughput region. These policies consider only the theoretical throughput and do not account the lost in throughput due to the time complexity of implementing an algorithm in practice. Therefore, we propose a novel concept called effective throughput to characterize the actual throughput by taking into account the time complexity. Effective throughput can be viewed as the actual transmitted data without including the control message overhead. Numerical results demonstrate that in practical scheduling, time complexity significantly affects throughput. The performance of throughput degrades when the time complexity is high.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2018.05a
• /
• pp.160-161
• /
• 2018

ITU-R Study Group Working Party 5B에서는 해상에서 자율운항선을 안전하게 운항하기 위해 자율운항선을 통한 제어센터-VTS, 제어센터-유인선 간의 정보교환이 이루어 질 수 있도록 Vessel traffic control voice relay의 기능을 제시하였다. 이에 자율운항선을 통해 제어센터-VTS, 제어센터-유인선 간의 원활한 정보교환이 가능하도록 사용자 기능 요구사항, 사용자 비기능 요구사항, 인터페이스 요구사항으로 분석함으로써 통신중계시스템 설계 및 각 운용 기기별 정보교환 체계를 구축하였다. 하지만 자율운항선-타 선박간의 충돌 위험성을 감지할 경우 충돌회피를 위한 흐름 및 통신중계시템을 활용한 메시지 처리과정은 설계되지 아니한 실정이다. 이에 본 연구에서는 액티비티, 제어흐름, 작업 흐름 등의 표현이 가능한 UML(unified modeling language)을 활용함으로써 항해단계 중 발생할 수 있는 상황별 시나리오를 제어 흐름 형태로 표현한 정보교환 메시지 처리 알고리즘을 제안하고자 한다.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.57.6-57
• /
• 2001

Jitter occurring during data communication creates difficulties in integrating a system. Such problems arise from using an event triggered communication protocol such as CAN(Controller Area Network) because it cannot be determined when a specific message will be transmitted. In order to avoid this problem, several time triggered communication protocols have been developed orare under development. Those protocols include TTP(TTTech) and TTCAN(BOSCH). But a time triggered communication protocol needs more hardware than an event triggered protocol and has more complicated software algorithm because data and time information goes through the existing data line ...

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.4 no.2
• /
• pp.71-88
• /
• 1994

메세지 전달시스템을 이용한 원거리 정보전달이 일반화되고 있다. X.400 메세지처리시스템 및 OSI 보안구조는 보안기능 및 서비스에 대한 표준을 개념적으로 정의하고 있으나, 메세지 전달시스템이 제공하는 보안서비스에 의존하여 중요정보를 송,수신하는 유저는 자신의 보안정책이 준수되기를 원한다. 이를 위해, 메세지 전달시스템과 유저의 독립적 또는 중첩된 2개의 다중 보안정책이 메세지 서버에서 준수되어야 한다. 메세지의 전송 및 프로세싱은 주체와 객체가 지닌 보안레이블이 강제적, 임의적, 마킹, 특권제어의 다중 보안정책에 부합될 때 액세스가 허용된다. 제안된 알고리즘이 메세지 서버에서 보안메카니즘으로 동작될 때, OSI 보안구조와 유저가 요구하는 보안요구조건이 만족됨으로서, 유저의 메세지가 안전하게 전송될 수 있다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.5 no.4
• /
• pp.856-873
• /
• 2011

Reversible watermarking is an open problem in information hiding field, with embedding the encoded bit '1' or '0' into some sensitive images, such as the law enforcement, medical records and military images. The technique can retrieve the original image without distortion, after the embedded message has been extracted. Histogram-based scheme is a remarkable breakthrough in reversible watermarking schemes, in terms of high embedding capacity and low distortion. This scheme is lack of capacity control due to the requirement for embedding large-scale data, because the largest hidden capacity is decided by the amount of pixels with the peak point. In this paper, we propose a reversible watermarking scheme to enlarge the number of pixels with the peak point as large as possible. This algorithm is based on an adaptive edge-guided interpolation, furthermore, hides messages by interpolation-error, i.e. the difference between the original and interpolated image value. Simulation results compared with other state-of-the-art reversible watermarking schemes in this paper demonstrate the validity of the proposed algorithm.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.30 no.3B
• /
• pp.138-143
• /
• 2005

This paper aims to optimize an access probe algorithm for the CDMA 2000 system. The incremental value of PWR_STEP increases as NUM_STEP as 1dBm±0.2 for access probe of the area with good receiving sensitivity when the mobile station transmits via access channel and does not receive any ACK message. However, for the area with weak receiving sensitivity, according to the algorithm of open-loop power control, the transmitting power amplifier becomes saturated and PWR_STEP incremental value keeps performing access probe to 0dBm±0.2. Therefore interference and battery consumption increases according to the transmission of the mobile station. We have optimized the access probe algorithm according to the receiving sensitivity. We transmit the incremental value of access probe power, with delaying as much RT slot value as indicated by IS-95C standard in case of good receiving sensitivity and with delaying RT+l slot value in case of weak receiving sensitivity. Simulation results showed that the proposed algorithm contributes to decrease of the interference and battery consumption according to the transmitting power of the mobile station and improves the call duration.

• Journal of Internet Computing and Services
• /
• v.13 no.4
• /
• pp.95-102
• /
• 2012

The development of applications for vehicular ad hoc networks (VANETs) has very specific and clear goals such as providing intellectual safe transport systems. An emergency warning technic for public safety is one of the applications which requires an intelligent broadcast mechanism to transmit warning messages quickly and efficiently against the time restriction. The broadcast storm problem causing several packet collisions and extra delay has to be considered to design a broadcast protocol for VANETs, when multiple nodes attempt transmission simultaneously at the access control layer. In this paper, we propose an early intelligent alert broadcasting (EI-CAST) algorithm to resolve effectively the broadcast storm problem and meet time-critical requirement. The proposed algorithm uses not only the early alert technic on the basis of time to collision (TTC) but also the intelligent broadcasting technic on the basis of fuzzy logic, and the performance of the proposed algorithm was compared and evaluated through simulation with the existing broadcasting algorithms. It was demonstrated that the proposed algorithm shows a vehicle can receive the alert message before a collision and have no packet collision when the distance of alert region is less than 4 km.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.13 no.8
• /
• pp.1729-1735
• /
• 2009

The hierarchical routing could cause a lot of energy consumption for transferring data by assigning hierarchical routes although actual nodes could be located in physically near spots. Also, when Node Failure or Association Error occurs, the Hierarchical routing could waste more energy to deliver the control messages. This paper evaluate performance of SHP(Shortest Hop Routing) algorithm that suggests short-cut routing algorithm using NL(Neighbor List) and Redirect_ACK message to improve problem of hierarchical routing algorithm. We do a computer simulation by the size of network, deployment of sensor nodes, sink position and POS. As a result of simulation, SHP has better performance than Zigbee Hierarchical routing and HiLow.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.32 no.11A
• /
• pp.1173-1181
• /
• 2007

A number of routing algorithms have been studied for wireless mobile ad-hoc network. Among them, the AODV routing algorithm with on-demand method periodically transmits hello message and monitors link state during data transmission in order to maintain routing paths. When a path is disconnected, a node that senses it transmits a RERR packet to the transmitting node or transmits a RREQ locally so that the path could be repaired. With that, the control packet such as a RREQ is broadcast, which causes the consumption of bandwidth and incurs data latency. This paper proposes a LRRLBP algorithm that locally repairs a path by predicting link state before disconnecting the path based on the AODV routing protocol for solving such problems. Intensive simulations with the results using NS-2 simulator are shown for verifying the proposed protocol.