• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.33-43
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• 2013

This paper proposes a distributed MAC protocol called Carrier Sensing Multiple Access with Collision Resolution (CSMA/CR) considering fully-connected single hop network environments for next-generation wireless LAN with high density of stations. The proposed CSMA/CR is compatible with the conventional MAC protocols by observing the operation of CSMA/CA and is able to detect a collision promptly without RTS/CTS exchange by applying the technique of CSMA/CD to wireless environments. Moreover, once a collision is detected, the dedicated resource is allocated to the next transmission and so the collision that may occur again is resolved. We investigate some implementation issues for the practicality of CSMA/CR and compare it with the typical distributed MAC protocols. The simulation results show that the proposed CSMA/CR has a low overhead as detecting a collision without the RTS/CTS exploitation and achieves always the best throughput regardless of the number of access stations, by using the reservation-based collision resolution technique.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.8
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• pp.84-97
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• 2012

In wireless sensor networks, cluster structure brings on many advantages such as load balancing, energy saving, and distributed key management, and so on. To transform a physical network into the cluster structure, sensor nodes should invoke a cluster formation protocol. During the protocol operation, if some nodes are compromised and they do not conform to the protocol, an inconsistency of membership in a cluster happen. This splits the cluster and consequently increases the number of clusters and decreases the number of members in the cluster. In this paper, we propose a scheme which well copes with such a problem. First, our scheme generates two hop clusters where hop distance between any two nodes is at most two. Besides, our scheme employs verification of two hop distant nodes to prevent the cluster split induced by compromised nodes. Last, our scheme mainly employs broadcast transmissions to reduce energy consumption of nodes. Simulation results have proven that our scheme reduces the number of clusters and more secure and energy-efficient than other scheme.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.3
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• pp.68-73
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• 2007

Recently, WSN(wireless sensor networks) consists of several sensor nodes in sensor field. And each sensors have the enforced energy constraint. Therefore, it is important to manage energy efficiently. In WSN application system, FEC(Forward error correction) increases the energy efficiency and data reliability of the data transmission. LDPC(Low density parity check) code is one of the FEC code. It needs more encoding operation than other FEC code by growing codeword length. But this code can approach the Shannon capacity limit and it is also can be used to increase the data reliability and decrease the transmission energy. In this paper, the author adopt Linear-Congruence method at generating parity check matrix of LDPC(Low density parity check) codes to reduce the complexity of encoding process and to enhance the energy efficiency in the WSN. As a result, the proposed algorithm can increase the encoding energy efficiency and the data reliability.

• Spatial Information Research
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• v.20 no.6
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• pp.119-127
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• 2012

u-City is next generation city which can innovate functions of city. It can realize increase of convenience, improvement of life quality and safety guarantee by convergence of information technologies and ubiquitous service with urban space. Market of u-City is in range of rapid growth and u-City can make enormous synergy effects by accompanying construction technologies with spatial information, sensor technologies, communications network and related equipments. In this study, we analyzed the domestic/abroad status, researches and element technologies involved in u-City. And, we suggested overseas expansion strategy of u-City such as selection and analysis of target nations, packaging method of u-City service models and application of BIM/GIS connection technologies in terms of u-City construction and operation.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.5
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• pp.161-167
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• 2012

Portable devices such as smartphones with built-in wireless LAN to the prevalence of anyone using. But the wireless Internet connection and positioning services are limited to high-quality wireless service, they may not be available. Thus, wireless LAN infrared sensor in the same way as with angry alternative way wireless capabilities of the application automatically identify the location of the Sensor application as an alternative method is proposed. Thus, wireless LAN, such as infrared sensors and other alternzative methods of wireless features in a way where the application can recognize and automatically recognize the sensor application as an alternative method is proposed. Sensor is signals between wireless LAN and access points using the sensitivity, WLAN antenna with omni-directional signal output operation of the sensor is assumed to be recognize this by putting a direction to obtain through the proposed algorithm, Sensors such as photo-coupler without direct recognition sensor, wireless LAN and access points, the same function as the connection between the sensitivity to perform its function was to utilizing.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 1999.12a
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• pp.66-71
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• 1999

For given 3D geographic data which is usually of DEM(Data Elevation Model) format, we have to represent and manipulate the data in various ways. For example, we have to draw a part of them in drawing canvas. To do this we give users a way of selecting area they want to visualize. And we have to give a base tool for users to select the local area which can be chosen for some geographic operation. In this paper, we propose a 3D data processing method for representation and manipulation. The method utilizes the major properties of DEM and TIN(Triangular Irregular Network), respectively. Furthermore, by approximating DEM with a TIN of an appropriate resolution, we can support a fast and realistic surface modeling. We implement the structure with the following 4 level stages. The first is an optimal resolution of DEM which represent all of wide range of geographic data. The second is the full resolution DEM which is a subarea of original data generated by user's selection in our implemeatation. The third is the TIN approximation of this data with a proper resolution determined by the relative position with the camera. And the last step is multi-resolution TIN data whose resolution is dynamically decided by considering which direction user take notice currently. Specialty, the TIN of the last step is designed for realtime camera navigation. By using the structure we implemented realtime surface clipping, efficient approximation of height field and the locally detailed surface LOD(Level of Detail). We used the initial 10-meter sampling DEM data of Seoul, KOREA and implement the structure to the 3D Virtual GIS based on the Internet.

• Journal of the Korea Society of Computer and Information
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• v.16 no.10
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• pp.33-43
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• 2011

Recently, advances in mobile communication and location identifying technology of the moving object is evolving. Therefore, the location-based services based on request for service have increased and a variety of the indexing for the position management of moving objects has been studied. Because the index based on Euclidean space are no restriction of movement, it is difficult to apply to the real world. Also, there is additional cost to find adjacent road segments in road networks-based indexing. Existing studies of fixed static objects such as buildings or hospitals are not considered. In this paper, we propose an efficient road networks-based indexing for management of current positions. The proposed indexing partitions road networks by grids and has integrated road connection informations and manage separated extra indexing for fixed static objects. Through the experiment, we show that the proposed indexing based on road networks improves the performance of operation for search or update than existing indexing.

• Journal of the Korea Society of Computer and Information
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• v.19 no.12
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• pp.123-132
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• 2014

In this paper, we study the verification techniques for OS integrity that can be more fatal than applications in case of security issues. The dissemination of smartphones is rapidly progressing and there are many similarities of smartphones and PCs in terms of security risks. Recently, in mobile network environment, there is a trend of increasing damages and now, there are active researches on a system that can comprehensively respond to this. As a way to prevent these risks, integrity checking method on operation system is being researched. As most integrity checking algorithms are classified by verification from the levels before booting the OS and at the time of passing on the control to the OS, in which, there are minor differences in the definitions of integrity checking or its methods. In this paper, we suggests the integrity verification technique of OS using a boot loader and a physically independent storing device in the mobile device.

• 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.

• Journal of Korea Port Economic Association
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• v.33 no.4
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• pp.37-58
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• 2017

The implicit assumption of port selection studies based on survey and respondents' perceptions is that the preference of the port selection attributes is proportional to the selection behavior. Further, the straight lines of the port selection attributes could also have non-linear properties. This study confirms nonlinear characteristics of selection attributes by using Kano model. The findings of this study showed that several properties of carriers were evaluated as nonlinear characteristics, such as the intermodal links and network accessibility, and size of port and terminal. Hence, port service providers such as port authorities and terminal operating companiesl, should construct a port operation strategy that reflects the non-linear port selection characteristics of shipping companies. Since this study aimed at exploring the forms of port selection characteristics, long-term additional verification studies on ports and stakeholders at domestics and abroad were needed. The Kano model and importance-selection analysis method used for analysis and strategy establishment also need to be improved to capture evident characteristics and to present strategic guidelines.