• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.9A
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• pp.729-736
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• 2005

In this paper, we introduce a new approach for the design of uplink sub-channel allocation and power control in the High-speed Portable Internet system that is based on OmMAnDD scheme. In OFDMA system, because the number of allocated sub-channel in mobile station varies from one to the whole sub-channel as in base station while mobile station's transmit power is lower than that of base station, full loading range(FLR) constraint occurs where whole sub-channel can be used and the conventional open-loop power control scheme can not be used beyond FLR. We propose a new scheme that limits the maximum sub-channel allocation number and uses power concentration gain(PCG) depending on location of mobile station, which is based on ranging in OfDMA system. Simulation results show that the proposed scheme extends the uplink coverage to the entire cell service coverage area, provides solutions for optimum utilization of radio resource and enables open-loop power control beyond FLR without extra hardware complexity.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4B
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• pp.303-310
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• 2006

In sensor network environments, a sensor node has a limited power because of their resource constraints. Therefore it is important to efficiently use its power in sensor networks. Power consumption of sensor node is closely related to its amount of transmission data. So, we need to reduce the transmission data in order to minimize the power consumption. And sensor networks are inherently unreliable because radio transmission can fail, node can move, and so on. In this paper, we propose the reliable data aggregation protocol in order to these problems. This protocol performs the routing and the query inserting process at the same time to minimize the packet loss caused by network changes. And, this protocol removes the unnecessary routing caused by the periodic routing without query. Additionally, we suggest the countermeasure algorithm against the frequent errors in sensor networks.

• The KIPS Transactions:PartA
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• v.18A no.3
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• pp.115-122
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• 2011

It is very hard to obtain a general algorithm for solution of all the constraint satisfaction optimization problems. However, if the whole problem is separated into subproblems by characteristics of decision variables, we can assume that an algorithm to obtain solutions of these subproblems is easier. Under the assumption, we propose a problem classifying rule which subdivide the whole problem, and develop backtracking algorithms fit for these subproblems. One of the methods of finding a quick solution is efficiently arrange for any order of the search tree nodes. We choose the cluster head positioning problem in wireless sensor networks in which static characteristics is dominant and interference minimization problem of RFID readers that has hybrid mixture of static and dynamic characteristics. For these problems, we develop optimal variable ordering algorithms, and compare with the conventional methods. As a result of classifying the problem into subproblems, we can realize a backtracking framework for systematic search. We also have shown that developed backtracking algorithms have good performance in their quality.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.2A
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• pp.83-94
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• 2012

Various wireless communication devices or network such as WRAN and WLAN will coexist in the TVWS(TV White Space). Because of this coexistence, the wireless devices which use the TVWS have to avoid interfering to not only licensed TV receiver and wireless microphone but also homogeneous or heterogeneous TVBD(TV Band Device)s. In this paper, we propose two frequency sharing methods for the coexistence of WLAN and WRAN in terms of interference reduction and throughput enhancement in both homogeneous and heterogeneous networks. One is the WRAN spectrum etiquette to provide more wide bandwidth for WLAN users and the other is the WLAN frequency selection methods to improve the throughput performance. The simulation results have confirmed the throughput improvement of the proposed methods. Moreover, the proposed methods is also applicable to improve the throughput performance and reduce interference of similar systems working in a cognitive manner.

• Korean Journal of Agricultural Science
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• v.38 no.3
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• pp.583-591
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• 2011

Status survey on short-term agricultural machinery rental business was conducted to provide basic data for effective and sustainable implementation of the rental system. Selected survey samples were 34 rental management institutions such as city and county level government offices and agricultural technology development centers, and Primary Agricultural Cooperatives. Survey was conducted through mailing of questionnaire papers and direct interviews with the officers in charge of the agricultural machinery short-term rental management. Number of agricultural machinery retained by the 34 management institutions for the machinery rental business was 3,699, and numbers of the machinery were 1630 for upland crops, 929 for rice, 542 for orchard farming, 274 for animal husbandry, and 324 for common use. Regarding size of warehouse for rental agricultural machinery, 50% of the institutes were less than 660 $m^2$, 26.5% were greater than 993 $m^2$, and 23.5% were between 663 and 990 $m^2$. Institutes maintaining machinery washing facilities were only 10 (29%) among the 34 rental management institutions. Agricultural machinery rental business was advertised to farmers by 91% of the institutes, and the methods were leaflet (35.2%), village broadcasting (26.5%), call-up education (23.6%), and TV and radio (14.7%). Major contents of the advertisement were rental procedure (52.9%), rental machinery (26.5%), and rental cost (20.6%).

• Journal of the Korea Society of Computer and Information
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• v.24 no.12
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• pp.43-50
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• 2019

In this paper, we designed a dynamic TDMA scheme for smooth tactical data distribution in TDMA tactical datalinks. Since the existing tactical datalinks use fixed time radio resources, it is impossible to change the resource status according to network conditions during operation. To overcome these limitations, we designed, implemented, and simulated the DTDMA processing and related messages such as initial timeslot allocation, intermediate time slot allocation, time slot return, and timeslot retrieval. As a result, it was shown that the method of effectively allocating and using timeslot resources according to the situation is applicable. Therefore, we will continue research to manage DTDMA communication on tactical data link in the future.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.7
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• pp.3529-3533
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• 2012

Objectives: To investigate the current prevalence and knowledge of cervical cancer, breast cancer and reproductive tract infections (RTIs) in rural Chinese women, and to explore the acceptance and feasibility of implementing a combined screening program in rural China. Methods: A population-based, cross-sectional study was conducted among women aged 30 to 59 years old in Xiangyuan County, Shanxi Province from 2009 to 2010. Socio-demographic characteristics, knowledge of cervical cancer, breast cancer and RTIs, and the attitude toward single or combined screening were collected by an interview questionnaire. Each participant received a clinical examination of the cervix, breast and reproductive tract. Examinations included visual inspection, mammography, laboratory tests and pathological diagnosis. Results: A total of 1,530 women were enrolled in this study. The prevalence of cervical precancerous lesions, suspicious breast cancer, suspicious benign breast disease and RTIs was 1.4%, 0.2%, 14.0% and 54.3%, respectively. Cervicitis, trichomonas vaginitis, and bacterial vaginitis were the three most common RTIs among our participants. Television, radio broadcast, and public education during screening were the major source of healthcare knowledge in rural China. Moreover 99.7% of women expressed great interest in participating in a combined screening project. The affordable limit for combined screening project was only 50 RMB for more than half of the rural women. Conclusion: A combined screening program would be more effective and popular than single disease screening projects, while appropriate accompanied education and a co-pay model for its successful implementation need to be explored, especially in low-resource settings.

• Journal of Communications and Networks
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• v.7 no.2
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• pp.115-125
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• 2005

This paper discusses how to effectively design a next-generation wireless communication system that can possibly provide very high data-rate transmissions and versatile quality services. In order to accommodate the sophisticated user requirements and diversified user environments of the next-generation systems, it should be designed to take an efficient and flexible structure for multiple access and resource allocation. In addition, the design should be optimized for cost-effective usage of resources and for efficient operation in a multi-cell environment. As orthogonal frequency division multiple access (OFDMA) has turned out in recent researches to be one of the most promising multiple access techniques that can possibly meet all those requirements through efficient radio spectrum utilization, we take OFDMA as the basic framework in the next-generation wireless communications system design. So, in this paper, we focus on introducing an OFDMA-based downlink system design that employs the techniques of hybrid multiple access (HMA) and frequency group (FG) in conjunction with intra-frequency group averaging (IFGA). The HMA technique combines various multiple access schemes on the basis of OFDMA system, adopting the multiple access scheme that best fits to the given user condition in terms of mobility, service, and environment. The FG concept and IFGA technique help to reduce the feedback overhead of OFDMA system and the other-cell interference (OCI) problem by grouping the sub-carriers based on coherence band-widths and by harmonizing the channel condition and OCI of the grouped sub-carriers.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.6B
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• pp.483-488
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• 2012

With the fast growing data traffic, the performance of the convergent overlay network environment under the cognitive networking environment is crucial for the implementation of the efficient network structure. In order to achieve high capacity and reliable link quality in wireless communication of the overlay convergent networks with the cognitive networking based on the advanced capability of the mobile terminal, a Distributed Wireless Communication System (DWCS) can provide the capability of ambient-aware dual cell system's operation. This paper has considered virtual cell: the Dual Virtual Cell (DVC), and also proposes DVC employment strategy based on DWCS network. One is the Active Virtual Cell which exists for user's actual data traffic and the other is the Candidate Virtual Cell which contains a set of candidate antennas to protect user's link quality from performance degradation or interruption. The considered system constructs DVC by using cognitive ability of finding useful virtual signals. Also, for multi-user high-rate data transmission, the DWCS system exploits Space-Time Trellis Codes. The effects of changing environments on the system performance has been investigated thereafter.

• Convergence Security Journal
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• v.7 no.2
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• pp.81-89
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• 2007

Mobile computing environment that support so that can offer employees inside information that enterprise has always improves business productivity and fetches efficiency enlargement. In this paper, limit model that can process ERP information by real-time as easy and convenient always utilizing radio network and PDA, Mobile camera based on Mobile vision concept. Calculable information between seller and customer is supplied supplying real-time brand image and information by practical use of Enterprise Resource Planning doing based on Mobile. Technical development and commercialization that utilize mobility, enforcement stronghold, portability etc. that is advantage of Mobile communication are required. In this paper, mobility of precious metals.jewel field that use portable terminal equipment taking advantage of a Mobile technology is secured. Constructed Mobile vision system that satisfy photography and bar-code scan at the same time from Mobile camera.