• Journal of Communications and Networks
• /
• v.10 no.3
• /
• pp.287-296
• /
• 2008

The IEEE 802.11 wireless standard uses the carrier sense multiple access with collision avoidance (CSMA/CA) as its MAC protocol (during the distributed coordination function period). This protocol is an adaptation of the CSMA/CD of the wired networks. CSMA/CA mechanism cannot guarantee quality of service (QoS) required by the application because orits random access method. In this study, we propose a new MAC protocol that considers different types of traffic (e.g., voice and data) and for each traffic type different priority levels are assigned. To improve the QoS of IEEE 802.11 MAC protocols over a multi-channel CSMA/CA, we have developed a new admission policy for both voice and data traffics. This protocol can be performed in direct sequence spread spectrum (DSSS) or frequency hopping spread spectrum (FHSS). For voice traffic we reserve a channel, while for data traffic the access is random using a CSMA/CA mechanism, and in this case a selective reject and push-out mechanism is added to meet the quality of service required by data traffic. To study the performance of the proposed protocol and to show the benefits of our design, a mathematical model is built based on Markov chains. The system could be represented by a Markov chain which is difficult to solve as the state-space is too large. This is due to the resource management and user mobility. Thus, we propose to build an aggregated Markov chain with a smaller state-space that allows performance measures to be computed easily. We have used stochastic comparisons of Markov chains to prove that the proposed access protocol (with selective reject and push-out mechanisms) gives less loss rates of high priority connections (data and voices) than the traditional one (without admission policy and selective reject and push-out mechanisms). We give numerical results to confirm mathematical proofs.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.29 no.4
• /
• pp.100-106
• /
• 2006

We analyze a voice/data integrated traffic model of the cellular mobile communication system with hybrid guard channels for voice and handoff calls. In a multi-service integrated wireless environment, quality of service guarantee is crucial for smooth transportation of real time information. Real time voice traffic requires a guaranteed upper bounded on both delay and packet error rate, whereas data traffic does not. Voice traffic has high transmission priority over data packets. Thus one of the important problems is the design of admission control schemes which can efficiently accommodate the differential quality of service requirements. In this paper, a hybrid guard channel scheme is considered in which arriving calls are assigned channels as long as the number of busy channels in the cell is below a predetermined first threshold. When the number of busy channels reaches the first threshold, new originating data calls are queued in the infinite data buffer. Then reaches second threshold, only handoff calls are assigned the remaining channels and new originating voice calls are blocked. We evaluate the system by a two-dimensional Markov chain approach and generating function method and obtain performance measures included blocking probability and forced termination probability.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1995.10a
• /
• pp.1186-1190
• /
• 1995

This paper is focused on the formulation of explicit closed-form functions describing the performance measures of the general flexible manufacturing system (FMS)according to the strategy of material handling system(MHS). the performance measures such as the production rate, the production lead-time and the utilization rate of the general FMS are expressed, respectively, as the explicit closed-form functions of the part processing time, the service rate of the material handling system (MHS) and the number of machine tools in the FMS. For this, the gensral FMS is presented as a generalized stochastic Petri net model, then, the moment generating function (MGF) based approach is applied to obtain the steady-state probabity formulation. Based on the steady-state formulation, the explicit closed-form functions for performance measures of the probability FMS can be obtained. Finally, the analytical results are compared with the Petri net simulation results to verify the validity of the suggested method. The paper is of significance in the sense that it provides a comprehensive formula for performance measures of the FMS even to the industry engineers and academic reademic resuarchers who have no background on Markov chain analysis method or Petrinet modeling

• Proceedings of the Korean Fiber Society Conference
• /
• 2003.10a
• /
• pp.55-56
• /
• 2003

An old castle in a tranquil setting. At first glance, no-one would suspect that this was the backdrop for the research and services centre providing expertise from all areas of the textile-clothing supply chain, textile care and other associated sectors. The Hohenstein Institutes are a modern communications centre with the latest research equipment where highly qualified scientists carry out their research and exchange knowledge. This combination of high-calibre staff and the philosophy of the unity of research, training and application have guaranteed the Hohenstein team of their position as an internationally respected institution offering high levels of expertise in all areas of the textile-clothing chain. At the beginning of the 21st century, the team of scientists at Hohenstein made the research and development of high-tech textile and garment innovations their number one priority. They recognise a rapidly developing market for "intelligent textiles" and "Smart Clothes" capable of adapting their function to the existing environmental conditions. Clients for the research projects, which are often carried out in conjunction with other institutions and industry, are research associations, federal ministries, the European Union and numerous leading companies both in Germany and abroad. The Hohenstein Institutes dispose of four international offices at the moment: in Turkey (since 1996), USA (since 1999), Lima (since 2002) and Mexico (since 2003).

• Journal of Information Technology Services
• /
• v.19 no.2
• /
• pp.109-124
• /
• 2020

Facing the 4^th Industrial Revolution era, researches on artificial intelligence have become active and attempts have been made to apply machine learning in various fields. In the field of finance, Robo Advisor service, which analyze the market, make investment decisions and allocate assets instead of people, are rapidly expanding. The stock price prediction using the machine learning that has been carried out to date is mainly based on the prediction of the market index such as KOSPI, and utilizes technical data that is fundamental index or price derivative index using financial statement. However, most researches have proceeded without any explicit verification of the prediction rate of the learning data. In this study, we conducted an experiment to determine the degree of market prediction ability of basic indicators, technical indicators, and system risk indicators (AR) used in stock price prediction. First, we set the core parameters for each financial indicator and define the objective function reflecting the return and volatility. Then, an experiment was performed to extract the sample from the distribution of each parameter by the Markov chain Monte Carlo (MCMC) method and to find the optimum value to maximize the objective function. Since Robo Advisor is a commodity that trades financial instruments such as stocks and funds, it can not be utilized only by forecasting the market index. The sample for this experiment is data of 17 years of 1,500 stocks that have been listed in Korea for more than 5 years after listing. As a result of the experiment, it was possible to establish a meaningful trading strategy that exceeds the market return. This study can be utilized as a basis for the development of Robo Advisor products in that it includes a large proportion of listed stocks in Korea, rather than an experiment on a single index, and verifies market predictability of various financial indicators.

• Journal of Digital Convergence
• /
• v.12 no.6
• /
• pp.311-316
• /
• 2014

Social network server due to the popularity of smart phones, and data stored in a big usable access data services are increasing. Big Data Big Data processing technology is one of the most important technologies in the service, but a solution to this minor security state. In this paper, the data services provided by the big -sized data is distributed using a double hash user to easily access to data of multiple distributed hash chain based data processing technique is proposed. The proposed method is a kind of big data data, a function, characteristics of the hash chain tied to a high-throughput data are supported. Further, the token and the data node to an eavesdropper that occurs when the security vulnerability to the data attribute information to the connection information by utilizing hash chain of big data access control in a distributed processing.

• The Journal of the Korea Contents Association
• /
• v.18 no.6
• /
• pp.564-573
• /
• 2018

External environment of enterprises are rapidly changing brought about mainly by global competition, cost and profitability pressures, and emerging new technology. In particular, frequent change of customer requirements is a tough challenge to manufacturing company. To cope with these challenges, a production planning and scheduling (PP&S) function might be established to provide accountability for both customer service and operational efficiency. PP&S deals with short-term decision making in the production process of whole supply chain. The task of PP&S is to seek a balance between customer orders and limited resources. At present, many PP&S software solutions have been utilized in many enterprises to generate a realistic production plan and schedule efficiently. The aim of this paper is to analyze the PP&S functionalities and its system architecture from the perspective of SCM (Supply Chain Management), and propose the PP&S solution classification framework to facilitate the comparison among various solutions.

• International Commerce and Information Review
• /
• v.6 no.3
• /
• pp.321-349
• /
• 2004

Bolero Project initially had the support of TEDIS, and now is a joint-venture between SWIFT and IT Club. After the successful testing of an original pilot project, The Bolero Association was formed in 1995 by a group of interested cross industry companies. A Bolero Bill of Lading replicates the basic functions of a paper-based bill of lading via title registry service and core messaging platform. A Bolero Bill of Lading consists of BBL Text and Title Registry Record. A Tittle Registry Record carries out the function of a document of title and a BBL may be transferred by changing the roles of users in this Title Registry Record. TEDI Project had been conducted from the April 1999 to the September 2000 on the basis of the EDEN Project(Dec.97- Mar. 1999) and International Trade Guidances Project (Nov. 1998-Mar. 1999). Through TEDI Project, the RSP Model was introduced as e-trade solution like Bolero's Solution. The RSP Model Solution will be furnished through TC (Trade Chain) Server and RSP(Repository Service Provider) Server. The purpose of this paper is to study the problems and solutions in the pilot test of electronic Bill of Lading using TEDI's RSP and to promote the introduction of electronic Bill of Lading.

• Korean Journal of Agricultural Science
• /
• v.37 no.1
• /
• pp.161-170
• /
• 2010

In Korea, food material industry encounters the emerging market which results from the growth of food service industry and food processing industry. Food material suppliers think that the total sales in Korean market may be around 20 trillion won. However, very small numbers of studies about Korean food material industry have been conducted. This paper analyzes the current status of food material industry and the market structure in Korea, and presents several suggestions for the development of Korean food material industry as following: building up the function of fresh-cut in production area, improving market structure, settling down the cold-chain system, enforcing the certification program for food safety.

• Journal of the Korea Safety Management & Science
• /
• v.3 no.4
• /
• pp.181-191
• /
• 2001

Integrated Supply Chain Management is a important subject for all enterprise activities as include logistics/sales, transfer and storage, manufacturing, purchasing of materials. A recent customer wants to receive high level service of all parts as Qualify, Delivery, Cost and Product. Therefore, Enterprise effort to supply for customers needs use some techniques like Data Mining, POS, MIS. Inventory and Logistics cost is the highest expense of all cost from first supplier to final customer on supply routine. So, SCM's basic purpose is reduce to that cost. So that this paper explain necessary, background, concept of SCM, analyze several using methodology and function of main SCM solution, after propose to ATP model include arithmetic procedure, functions, input data for determines available due date.