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장근녕 新羅大學校 1999 論文集 Vol.47 No.-
Electronic commerce (E-commerce) is a new way of engaging in timeless activities interafcting, bartering and transacting with people and businesses. However, as in any other means of business, we cannot assume all players will abide by a code of moral conduct. The mere fact that business is being performed online over an insecure medium, for example the Internet, is enough to induce criminal activity. To this end, a number of protocols and technical solutions have been introduced to assure ind users and businesses of privacy and confidentiality in online transactions. The Secure Electronic Transaction (SET) is an imirging standard for secure credit card payments over the Internet. SET can be applied in a real-time environment such as a Web session or in a store-and-forward manner such as electronic mail. This paper introduces SET, and analyzes security assurance technologies such as hash function. encryption algoritm and identity certification technology used in SET and other E-commerce protocols. Finally, thes paper analyzes electronic signature techniques such as digital and dual signatures being used in SET, and digital multisignature, proxy signature, group signature and group membership proof which have to be additionally considered in implementing complete and secure E-commerce.
장근녕 한국경영과학회 1997 韓國經營科學會誌 Vol.22 No.4
In tis paper, an efficient dynamic channel assignment scheme is suggested, which consists of two types of channel allocation strategies: ordinary channel allocation strategy and channel reallocation strategy. An analysis on the handoff probabilities of handoff and new calls is also performed, and using the analyzed handoff probability, the presented scheme is compared with other existing schemes in terms of three types of blocking probabilities - new call blocking probability, handoff call blocking probability, and net work blocking probability (incomplete service probability). Simulation results show that the presented scheme significantly reduces those blocking probabilities over the existing schemes. Furthermore, the scheme has much smaller number of reallocations than other schemes.
장근녕 한국경영과학회 1995 經營 科學 Vol.12 No.3
The future demand of the satellite broadcasting service is analyzed through the competitive diffusion model. Diffusion rates of the satellite broadcasting service in the case that the decreasing effect due to the cable TV service is considered are smaller than those in the independent case. Diffusion rates of the satellite broadcasting service are shown to become different according to environmental conditions.
CDMA 이동통신시스템을 위한 QoS 기반 최적 전송출력/전송률 할당 체계
장근녕 한국경영과학회 2003 한국경영과학회지 Vol.28 No.4
This paper studies power and rate control for data users on the forward link of CDMA system with two cells. The QoS for data users is specified by delay and error rate constraints as well as a family of utility functions representing system throughput and fairness among data users. Optimal power and rate allocation problem is mathematically formulated as a nonlinear programming problem, which is to maximize total utility under delay and error rate constraints, and optimal power and rate allocation scheme (OPRAS) is proposed to obtain a good solution in a fast time. Computational experiments show that the proposed scheme OPRAS works very well and increases total utility compared to the separate power and rate allocation scheme (SPARS) which considers each cell individually.
MF-TDMA 광대역 위성시스템을 위한 QoS 기반 최적 타임슬롯 할당 체계
장근녕,이기동,박유진 한국경영과학회 2004 韓國經營科學會誌 Vol.29 No.4
In this paper, we consider broadband satellite systems using MF-TDMA(Multi-Frequency Time Division Multiple Access) scheme. First, we analyze return link, superframe structure, and QoS(Quality of Service) parameters in broadband satellite systems, and mathematically formulate the QoS-based optimal timeslot allocation problem as a nonlinear integer programming problem for broadband satellite systems with clear-sky and rain-fade satellite terminals, and multiple data classes. Next, we modify the proposed problem to solve it within in a fast time, and suggest the QoS-based optimal timeslot allocation scheme. Extensive simulation results show that the proposed scheme finds an optimal solution or a near optimal solution within 5ms at Pentium IV PC.
Prioritized Channel Allocation for Cellular Mobile Systems Using Simulated Annealing
Chang, Kun-Nyeong 한국경영과학회 1998 한국경영과학회지 Vol.23 No.3
Under the cutoff priority discipline, the prioritized channel allocation problem is formulated, which minimizes the overall blocking probability while ensuring the co-channel interference constraints. To deal with the problem more conveniently, the concept of pattern is used. A simulated annealing approach is applied to the problem, and computational experiments show that a high-quality solution is obtained.
Efficient Channel Management for Cellular Mobile Communication Systems
Chang, Kun-Nyeong,Kim, Sehun 한국경영과학회 1994 한국경영과학회 학술대회논문집 Vol.- No.2
The minimum span problem (MSP) and minimum blocking problem (MBP) for cellular mobile systems with nonuniform traffic distributions are considered. MSP minimizes the span, i.e., the number of channels, necessary to satisfy a given grade of service (GOS) for the system subject to the co-channel, adjacent and co-site interference constraints. MBP minimizes the average blocking probability of the system subject to the interference constraints, given the number of available channels. In this paper, we suggest an efficient heuristic algorithm for MSP which sues a GOS value updating scheme, and compare the algorithm with existing other ones. Computational experiments show that this algorithm provides solutions with much smaller span than others. We also show that a simple modification of that algorithm provides encouraging computational results for MBP.
Improving Throughput and Packet Delay of Interactive Multimedia Satellite Networks
Kun-Nyeong Chang,Ki-Dong Lee,Tho Le-Ngoc 에스케이텔레콤 (주) 2011 Telecommunications Review Vol.21 No.1
In Geostationary Earth Orbit (GEO) satellite networks, the delay of packets queued in satellite terminals in the return-link is a critical factor to degrading the quality-of-service. In this paper, we suggest two unbiased traffic forecasting models, which belong to a family of commonly used time-series models, based on the first-and secondorder variations of traffic, and develop new Demand Assignment Multiple Access (DAMA) protocols based on the proposed traffic forecasting models in order to improve the delay of packets. We compare the delay and throughput performance of the proposed DAMA protocols with that of two previous protocols under the two traffic models,SupFRP and PowON_PowOFF models, for various parameters setups. Simulation results show that the proposed protocols significantly improve the delay compared to previous DAMA protocols. This implies that, in the proposed protocols, by accurate estimation of traffic demand, valuable resources are more properly allocated to satellite terminals so that the amount of resources allocated, but not actually used for traffic transmission, can be reduced: ultimately, this improves the transmission delay of those terminals with higher traffic demand.