• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.11 no.1
• /
• pp.3-12
• /
• 2001

In this paper, a synchronized stream encryption system for secure link layer communication in a radio channel is designed. Interleaving scheme which is used to enhance the transmission performance over a fading channel is applied to the encrypted information. A designed synchronous scream cipher system consists of a keystream generator, a synchronization pattern generator and a session key generator. The structure of a synchronous stream cipher system with periodic synchronization is composed of the encrypted information which consists of a synchronization pattern, an error correcting coded session key, an encrypted data in a period of synchronization. In this paper, interleaving scheme using dynamic allocation a1gorithm(DAA) is applied the encrypted information. The BER of the DAA has been slightly higher than that of the SAA(static allocation algorithm).

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.23 no.4
• /
• pp.491-498
• /
• 2012

Recently, many papers have been proposed in order to improve the OFDM system performance in T-DMB DOCR (Digital On Channel Repeater), by using removing the feedback signal so that the transmitter power can be increased or by using the equalizer to remove ICI. Despite these efforts, however, signal quality at the receiving terminal has not been improved because of constellation smearing in T-DMB DOCR. In this paper, in order to suppress constellation smearing, we propose an effective equalizer algorithm that can improve system performance. We perform adaptive channel estimation and non-coherent decision directed noise cancellation method that can estimate the channel subsequently during data symbols period in the frequency domain. So we can obtain better quality of the signal at the receiving terminal. In order to secure QoS(Quality of Service) required in T-DMB handsets, we evaluate SNR and BER in T-DMB DOCR(Digital On Channel Repeater) and verified by simulation. In this simulation results, this system is satisfied the performance of BER=$10^{-5}$ at less than SNR=14 dB at the receiver after compensation of phase noise -18 dBc.

• Journal of Distribution Science
• /
• v.9 no.4
• /
• pp.63-73
• /
• 2011

The relationship between buyers and sellers is changing into a long-term relationship. A number of distribution channel researchers have determined that the behavior of distribution channel members can be characterized by relational exchanges. The members of relational distribution channels may be perceived as strategic partners; however, even within these arrangements, member asymmetries may exist, which can create unequal distributions of power and dependence. Thus, as all distribution channel members may not be equal in power, it is possible that a less-dependent channel leader may emerge. Therefore, leadership in distribution channels is a very important variable. Distribution channel leadership can be defined as the activities undertaken by the distribution channel leader to influence the marketing programs and strategies of channel members. A distribution channel's performance is influenced by the leadership style of the channel leader. Although research on channel leadership styles can be broadly categorized, many researchers have dealt with analyzing distribution channel leadership by using the power-influence approach, which includes looking at variables, such as power, power base, and influence strategies. Moreover, they have examined the direct relationship between leadership styles and performance. Many distribution channel scholars have attempted to justify the application of leadership styles identified in alternative leadership theories to the inter-organizational context of distribution channels. They have made suggestions regarding how great the usefulness of leadership style as a strategy is to secure the compliance of distribution channel members and have conceptually and empirically linked it to channel-related phenomena, such as manifest conflict, cooperation, channel efficiency, and effectiveness. However, as few empirical studies have examined the antecedents and consequences of leadership styles, research on leadership style can be considered nascent. Thus, it is required to investigate the antecedents and consequences of the leadership style of a distribution channel leader. This study aims to empirically identify whether there are influences of the antecedents of leadership on two different leadership styles, and to reveal whether these leadership styles induce any consequences. The research subjects were 220 franchisees. Research findings are as follows: First, the results show a positive effect of technological capability on transformational relationships. However, it does not have a significant effect on transactional leadership. Second, innovation-oriented organizational culture has negatively influenced both leaderships. However, task-oriented organizational culture positively and significantly influenced both forms of leadership. Third, the ethics of leaders has influenced both leadership styles positively and significantly. Fourth, regarding consequences, transformational leadership strengthens financial performances, whereas it weakens relational citizenship behaviors. However, transactional leadership positively influences relational citizenship behavior whilst negatively affecting financial performance.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.1
• /
• pp.132-139
• /
• 2016

This study was carried out near the waters of Jango port, Dangjin-gun, Chungcheongnam-do by utilizing 10kHz carrier frequency, for the purpose of measurement and analysis of underwater channel environment of the Western sea. For the measurement of horizontal channel environment, the separation distance between transmitter and receiver is made differently in the range between 10m and 4000m. Meanwhile, for the measurement of vertical channel environment, transmission and receiving side ships are fixed as contacted each other and measured differently depending on their depth of submergence. In this study, the Coherence Bandwidth and the Coherence Time were estimated by analyzing the Power delay profile of the real sea based on the measured data, and analyzing the doppler frequency through frequency conversion of received tone-signal, respectively. This study is expected to become a base study in carrying out the frame design for underwater communication to improve the communication and secure the reliability of communication in future underwater channel environment.

• Journal of Digital Convergence
• /
• v.14 no.10
• /
• pp.261-269
• /
• 2016

This paper aims to propose a novel technology of network convergence to provide ultra high speed internet services over CATV networks, by which a CMC(cable modem concentrator) and CM(cable modem) of 1Gbps level are designed. This technology not only lowers the production cost in comparison to the existing bonding technology with DOCSIS specification but also enables the adjustment of data speed based on the channel bandwidth. According to the experiments, when convolutional code rate with 128QAM is changed to 1/2, 2/3, 3/4 and 7/8, the data recorded the maximum transmission speed of up to 299 Mbps at the zero error rate. As the convolutional code rates with 256QAM is increased, it showed 334Mbps at the error rate of $10^{-5}$. Based on the findings of this paper, if we secure the channel bandwidth of 200MHz and adjust the modulation order of QAM and the convolution code rate depending on the channel status, we can get the transmission speed of more than 1Gbps, which is much more competitive in its function and price than the existing technology based on DOCSIS.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.35 no.5
• /
• pp.369-374
• /
• 2007

Unsteady aerodynamic characteristics of the wing with flaperon flying over nonplanar ground surface are investigated using a boundary-element method. The time-stepping method is used to simulate the wake shape according to the motion of the wing and flaperon over the surface or in the channel. The aerodynamic coefficient according to the periodic motion of the flaperon is shown as the shape of loop. The rolling moment coefficient of the wing flying in the channel is same as that of the wing flying over the ground surface. The variation range of pitching moment is wider when the wing flies in the channel than over the ground surface. The present method can provide various aerodynamic derivatives to secure the stability of superhigh speed vehicle flying over nonplanar ground surface using the present method.

• Journal of Navigation and Port Research
• /
• v.38 no.6
• /
• pp.689-694
• /
• 2014

The Korean government has introduced and enforced maritime traffic safety assessment to secure traffic safety since 2010. The maritime traffic safety assessment is needed by law to design a new port or modify an existing one. According to Korea Maritime Safety Act, in the assessment the propriety of marine traffic system consists of the safety of channel transit and berthing/unberthing maneuver, safety of mooring, and safety of marine traffic flow. The safety of channel transit and berthing/unberthing maneuver can be evaluated only by ship-handling simulation. The ship-handling simulation is carried out by sea pilots working with the port concerned. The vessel's proximity measure is an important factor to evaluate traffic safety. The proximity measure is composed of vessel's closest distance to channel boundary and probability of grounding/collision. What is more, the probability of grounding becomes important. According to central limit theorem, a sample has a normal distribution on condition that its size is more than 30. However, more than 30 simulation runs bring about the increase of assessment period and difficulty of employing sea pilots. Therefore this paper is to find out minimum sample size for evaluating vessel's proximity. First sample sets of size of 3, 5, 7, 9 etc. are selected randomly on the basis of normal distribution. And then KS test for goodness of fit and t-test for confidence interval are applied to each sample set. Finally this paper decides the minimum sample size. As a result this paper suggests the minimum sample size of 5, that is, the simulation of more than five times.

• Journal of Broadcast Engineering
• /
• v.16 no.3
• /
• pp.490-500
• /
• 2011

The channels of domestic FM broadcast are needed to provide various kinds of new broadcasting services. However, available channels are limited and saturated. The channel interval of FM broadcast is changed from 200 kHz to 100 kHz to maximize utilization efficiency of scarce broadcast spectrum at all over the world. Also, there are many researches such as IBOC(In Band On Channel) and DRM+(Digital Radio Mondial+) that is to allocate the digital signal beside analog bandwidth. But output power is decrease to avoid interference between adjacent radio stations. In this paper, we analyzes the problems of the protection ratio which is decided in 1986 and we propose method to improve about 7~10dB significantly the protection ratio according to the recent DSP(Digital Signal Processing) techniques without loss of both transmission power and broadcast quality. In addition, we examined the possibility of securing two times available channels by reducing minimum frequency interval from 800 kHz to 400 kHz or 600 kHz in the equal site.

• The KIPS Transactions:PartC
• /
• v.17C no.1
• /
• pp.37-46
• /
• 2010

In an IPTV system, the rights of the content and service provider can be protected by using Conditional Access System (CAS) and Digital Right Management (DRM). In case of the CAS, only the authorized user who has structured authentication keys can decrypt the encrypted content. However, since the CAS establishes a secure channel only between content provider and Smart Card (SC), it cannot protect the system against McCormac Hack attack which eavesdrops on unsecure channel between SC and Set-Top Box (STB) and SC cloning attack. In this paper, we propose a robust multi-STB assisted SC / STB authentication protocol which can protect the IPTV system against not only McCormac Hack attack, but also SC cloning attack. The previous works which bind a STB and a SC during the SC registration phase against the SC cloning attack does not support multi-STB environments. The proposed system which dynamically updates the STB information in subscriber management system using the bi-directional channel characteristic of IPTV system can support the user's multi-STB device effectively.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.11
• /
• pp.5872-5878
• /
• 2013

This study provides two channel structure and two factor authentication. First, a purchasing request by Internet and then user certification and a settlement approval process by mobile communication. Second, it support that proposal protocol utilize a partial factor value of stored in users smartcard, smart phone and password of certificate. Third, storage stability is improved because certificate store in smartcard. Finally, proposal protocol satisfy confidentiality, integrity, authentication, and non- repudiation on required E-commerce guideline. In comparative analysis, Efficiency of the proposal protocol with the existing system was not significantly different. But, In terms of safety for a variety of threats to prove more secure than the existing system was confirmed.