• Journal of KIISE:Information Networking
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• v.34 no.6
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• pp.435-445
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• 2007

Snoop protocol is one of the efficient schemes to compensate TCP packet loss and enhance TCP throughput in wired-cum-wireless networks. However, Snoop protocol has a problem: it cannot perform local retransmission efficiently under the bursty-error prone wireless link. To solve this problem, SACK-Aware-Snoop and SNACK mechanism have been proposed. These approaches improve the performance by using SACK option field between base station and mobile host. However in the wireless channel with high packet loss rate, SACK-Aware-Snoop and SNACK mechanism do not work well because of two reason: (a) end-to-end performance is degraded because duplicate ACKs themself can be lost in the presence of bursty error, (b) energy of mobile device and bandwidth utilization in the wireless link are wasted unnecessarily because of SACK option field in the wireless link. In this paper, we propose a new local retransmission scheme based on Cross-layer approach, called Cross-layer Snoop(C-Snoop) protocol, to solve the limitation of previous localized link layer schemes. C-Snoop protocol includes caching lost TCP data and performing local retransmission based on a few policies dealing with MAC-layer's timeout and local retransmission timeout. From the simulation result, we could see more improved TCP throughput and energy efficiency than previous mechanisms.

• Journal of the Korean Association of Geographic Information Studies
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• v.19 no.1
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• pp.106-119
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• 2016

Flood risk map, flood damage map, disaster information map, inundation trace map are involved with the cartographic analysis of flood inundation based on prevention, preparation, restoration, response from natural disasters such as flood, flooding, etc. In this study, the analysis for channel and basin characteristics Chungju dam to Paldang dam of South han river after four river project. Flood scenario is selected to take advantage of design flood level of schematic design for river. Flood inundation of one dimensional non-uniform flow by using HEC-RAS with basin characteristics is accomplished and two dimensional unsteady flow was interpreted by using FLUMEN. Frequency analysis is carried out about each abundance of South han river for 100 year period, 200 year period and 500 year period. Flooding disaster area of 100 year period on 0.5m damage functions is 2378.8ha, 200 year period on 0.5m damage functions is 3155.2ha, 500 year period on 0.5m damage functions is 3995.3ha respectively. It will be significant data for decision making to establish inundation trace map for providing basic plan for river maintenance, land use plan, flood protection plan, application plan and getting information of flood expectation area.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.43 no.10 s.352
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• pp.35-45
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• 2006

Coordinator is defining so that function as most trust center that is point in security in ZigBee Alliance. Because must do height connection with coordinator in device signing to PAN newly, coordinator has shortcoming that subordinate is revealed to danger directly to Centered and cattish device. When do height connection some device, do not become problem, but if network is huge, coordinator's subordinate shall increase as traffic quantity which happen in coordinator increases. Also, in ZigBee security to link network kina of transmission and mutually certification in ZigBee Alliance standard include, but I do not provide method to deliver master key in each node safely. Because process that transmit master key passes through channel that do not secure, master key has shortcoming that is revealed directly. In this paper, I suggested Parent-Child key establishment algorithm to solve these problem. Proposed algorithm consists of two structures. Master key establishment algorithm and device that sign to PAN newly that can use one-way Hash chain and transmit master key safety are consisted of Parent-Child network key establishment algorithm that do child node and parent node key establishment as can do key establishment efficiently. Method that device proposes in case method that propose in case have master key establishment time was shown better performance $200{\sim}1300ms$ than existing method, and device does not have master key than existing method height connect time about $400{\sim}500ms$ better performance see.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.12
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• pp.39-47
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• 2010

This paper proposes a fully-utilized block-based 2D DWT architecture, which consists of four 1D DWT filters with two-channel QMF PR Lattice structure. For 100% hardware utilization, we propose a new method which processes four input values at the same time. On the contrary to the image-based 2D DWT which requires large memories, we propose a block-based 2D DWT so that we only need 2MN-3N of storages, where M and N stand for filter lengths and width of the image respectively. Furthermore, the proposed architecture processes in horizontal and vertical directions simultaneously so that it computes the DWT for an $N{\times}N$ image within a period of $N^2(1-2^{-2J})/3$. Compared to existing approaches, the proposed architecture shows 100% of hardware utilization and high throughput rate. However, the proposed architecture may suffer from the long critical path delay due to the cascaded lattices in 1D DWT filters. This problem can be mitigated by applying the pipeline technique with maximum four level. The proposed architecture has been designed with VerilogHDL and synthesized using DongbuAnam $0.18{\mu}m$ standard cell.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.4
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• pp.506-519
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• 1999

An adaptive array antennal and a CCI canceller have been considered as techniques for cancelling Multi-User Interference(MUI) in Direct Sequence Code Division Multiple Access(DS-CDMA) system. These techniques have different problems respectively in the process of cancelling MUI as the number of users increases. For that reason, the scheme which can cancel MUI effectively by compensating for the problems of each of the techniques has been required. For the scheme, the technique to connect an adaptive array antenna and a CoChannel Interference(CCI) canceller in cascade form has been studied. In the existing study about the cascade connection method, the effect of cancelling MUI about two interference signals is analyzed, but the analysis for the quantitative BER(Bit Error Rate) improvement according to the number of users is not considered. Therefore, in this paper, we have analyzed the degree of BER performance improvement quantitatively according to the number of users by introducing the receiving system, which connects an adaptive array antenna and a CCI canceller to a DS-CDMA system in cascade form. For the method of analyzing the performance, we have performed the theoretical analysis and the simulation, considering the case of adopting only an adaptive array antenna and of cascade connection respectively, and having compared and analyzed the results. From the results, it is confirmed that in the case of adopting only an adaptive array antenna, the problems occur in the process of cancelling MUI according to the number of users and the receiving direction of interference signals, and can be compensated by the cascade connection method. In conclusion, we have known that MUI is cancelled effectively by using the cascade connection method, and the much better BER performance improvement is obtained.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• v.29 no.1
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• pp.191-195
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• 2005

The port entry system of the inner harbor in Pyeongtaek (Asan) was planned as lock-gate in 'Master plan project on port planning in Asan industry base(1990)', but was changed to tidal harbor in 'Project maintaining Master Plan for comprehensive development of Pyeongtaek (Asan) port(2001)'. Accordingly, southern sea bank constructed under the lower part of Seohae-bridge will be removed so that inbound/outbound vessels for the inner harbor can navigate at all times. However, in the view of the safety on passing through the lower of Seohae-bridge, navigating conditions for the inner harbor will be restricted in the single-way of 50,000 DWT vessel and the two-day of vessel less than 30,000 DWT. Therefore, this study carried out the estimation of traffic congestion arising from these vessels with above restrictions after supposing annual inbound/outboubd vessel's numbers for loading and unloading cargo surveyed on the inner harbor.

• Korean journal of communication and information
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• v.43
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• pp.359-384
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• 2008

Nowadays, newspaper industry faces a crisis in terms of two aspects: First, in this multi-channel era, it has competed with the online journalism appearing in many digital media. Second, with the decrease of numbers of readers and political participation, the roles of newspaper has to be changed accordingly. The concept of civic journalism emerged as a solution in this context. The purpose of the study is to explore the factors in how journalists perceive the civic journalism. The Q-methodology was adapted to identify the factors composing of the belief, values, attitudes, ideas, and opinions toward the civic journalism. Total of 24 Q-sample (statements) were sorted by 27 P-sample (journalists) who were selected by their gender, years of service, and the like. The Quanl program finally produced 3 factors that were interpreted and named as follows: Factor I, the Complimentary Journalism, the civic journalism would fulfill the functions that traditional journalism has neglected. Factor II, the Alternative Journalism inducing the citizen's participation in the public areas. Factor III, the Functional Journalism, emphasizing dysfunction of the civic journalism.

• Journal of Applied Tourism Food and Beverage Management and Research
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• v.8
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• pp.123-144
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• 1997

This study, by setting the systems of room sale promotion, analyzing the actual status and the present working state with its center on the 'RHotel' that is a special grade-two hotel and the sales promotion activities of each type, intends to understand the presentstatus of the hotel and present its problems and the method for improvement. The strategy of salespromotion and the ineffectivenessof the system organization were found to be imminent in the sales promotion activities as its problems, and the importanceis being not attached to the actual substance rather than to the actualresults, such as the advertisement and publicity strategies, the irrationality of sales personnel controland its evaluation method, and therefore, the goal-oriented control is not being takenad its problems are emerging. Therefore, as an improvement plan, we ought to put the plan of the hotel merchandising into action for customers to buy what they want, the establishment of the customer-oriented sales promotionservice and the communication channel using the brand-new managerial skills, systemaizesales promotion method sand strategies, develop the organizational and systematic strategies develop the organizatinal and systemactic strategies and goods for the sake of the image-making and room sales promotion of hotels, develop the activation ways of flexible operation, and also need to develop the skills of sales promotion. Accordingly, by doing irrationalsales activities in the system and the promotion with its center on the sales promotion department, and it sis urgently required that we streng then the comodity developments fitting the hotel's traits, such as uniformpolicy of cost, mass-communicationactivities for sales promotion, the improvement of non-effectiveness, and advertisement of hotel items, and the publishing of public relation books. Therefore, the best weapon for hotels before other purchaseis to be discriminatized from other competitive hotel with theunderstanding of the psychology and activities of customers, and the communicatin with customers, and to set up organicprograms of sales promotionstrategies. Also we must promote our sales in accordance with the desire of new customers, gater the market information of customers, all the time, and systematize the facility improvement, managerial policy, business strategiescorresponding with the desire of customers. By doing so, we are able to seek, at the same time, both the satis faction of customers and the sales maximization of the hotels that will perfrom the activities of sales promotion and management.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1152-1160
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• 2004

OFDM technique was adopted as the standard of IEEE 802.1 la and it has been widely used for wireless LAN, European DVB/DAB system, Korean DMB system. In the standard of IEEE 802.11a the data packet is composed of two parts, preamble and data. Preamble is composed of short pilots and long pilots, which are used for synchronization and estimation of frequency offset and channel. We can also compensate phase noise effect in the transceiver by using above pilots. The phase noise is more complicate than frequency offset and seriously affects system performance. In this paper, we newly propose CPE and ICI simultaneous compensation method to compensate phase noise generated by transceiver oscillator and compare with previous studies. As results, phase noise effect can be significantly compensated by CPE cancellation method, PNS algorithm and our proposed CPE and ICI compensation method. Especially, the proposed CPE and ICI compensation method can achieve the best BER performance compared with original OFDM, CPE cancellation method and PNS algorithm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.12 s.103
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• pp.1171-1178
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• 2005

Multi-code code division multiple access(MC-CDMA) has been proposed for providing the various service rates with different quality of service requirement by assigning multiple codes and increasing the capacity. However, it suffers from the serious problem of high peak to average power ratio(PAPR). So, it requires large input back-off, which causes poor power consumption in high power amplifier(HPA). In this paper, we propose a new method that can reduce PAPR efficiently by constraint codes based on the opposite correlation to the incoming information data in MC-CDMA. PAPR reduction depends on the length and indices of constraint codes in MC-CDMA system. There is a trade-off between PAPR reduction and the length of constraint codes. From the simulation results, we also investigate the BER improvement in AWGN channel with HPA. The simulation results show that BER performance can be similar with linear amplifier in two cases: 1) Using exact constraint codes without input back-off and 2) a few constraint codes with small input back-off.