• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.689-692
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• 2021

This paper is a prior study to improve the efficiency of offloading based on mobile agents to optimize allocation of computing resources and reduce latency that support user proximity of application services in a Fog/Edge Computing (FEC) environment. We propose an algorithm that effectively reduces the execution time and the amount of memory required when extracting optimal moving patterns from the vast set of spatio-temporal movement history data of moving objects. The proposed algorithm can be useful for the distribution and deployment of computing resources for computation offloading in future FEC environments through frequency-based optimal path extraction.

• Journal of the Korean Institute of Landscape Architecture
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• v.47 no.2
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• pp.100-116
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• 2019

Urban green spaces, as a means to mitigate social problems and environmental risks, are getting more attention in evaluating urban environment. The inequity of green space distribution is becoming a major issue in urban planning and management. This study investigated the characteristics of green space in 3 districts (Jung-gu, Dongdaemun-gu, Seongdong-gu), that are composed of 46 administrative divisions in central Seoul, to analyze the environmental equity of urban green spaces. The correlations between the amount of green space, including the coverage of street trees, and the socioeconomic status of each administrative division were analyzed. To deduce the effects of plant coverage on the urban temperature regime, the relationship between the normalized difference of vegetation index (NDVI) and land surface temperature (LST) was analyzed. The research revealed that the mean NDVI of an administrative division was negatively correlated with the percentage of basic living recipients and disabled people. The LST of a division with low NDVI was higher due to the lack of green coverage. Such environmental inequities were closely related to residential building type, which was strongly affected by the economic status of residents. The LST of an apartment area was $2.0^{\circ}C$ lower than that of single-family houses and multi-housing areas. This is expected as the average NDVI of the apartment area was more than twice as high as the other environments considered in this study. The inequity can be exacerbated without urban planning which is deliberately designed to reduce it.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.05a
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• pp.214-217
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• 2001

This paper presents an implementation methodology of common Rf- integrated PCS base station system which, is capable of providing PCS services for 3 PCS carriers concurrently and wireless system performance evaluation data is shown. We have built up a common PCS base station system using a commonization module, which is consisted of a multi-channel combiner, duplexer, LNA, power divider, feeder line, and a common set of antennas. It was shown that the performance of the system within the total 30MHz PCS frequency range is uniformly acceptable and measured signal quality and coverage are equivalent to that of the individual PCS base station. It is expected that PCS carriers are able to save a huge amount of installation and maintenance expenses by installing and sharing this base station system. This paper forms a groundwork for deploying efficient and economical IMT-2000 network.

• Journal of the Institute of Electronics and Information Engineers
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• v.53 no.3
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• pp.163-169
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• 2016

To establish the equitable distribution of total energy load, a representative cluster based routing protocol LEACH selects cluster heads randomly in accordance with the pre-determined probability every round. But because the current energy level of sensor nodes is not considered, if a sensor node which has little residual energy is elected as a cluster head, it can not live to fulfil the role of cluster head which has big energy load. As a result, the first time of death of a node is quickened and the service quality of WSN gets worse. In this regard we propose a new routing method that, by considering the current energy of a cluster head and the distance between cluster heads and a base station, selects the sub cluster head for saving the energy of a cluster head. Simulation results show that the first time of death of a node prolongs, more data arrive at the base station and the service quality of WSN improves.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.20 no.5
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• pp.89-98
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• 2010

Wireless LAN (WLAN) is type of wireless service that has higher data transmission than current cellular networks. The usage is continually increasing. There are a lot of vulnerabilities in wireless network, due to the properties of the wireless environment, regardless of its popularity. IEEE announced the 802.11i security standard to solve these problems. The vulnerable point of messages used in the process of key distribution for 802.11i makes the target node attacked lose memory through continuous messages and blocks the legitimate WLAN service. In this paper, we proposed new schemes to solve this problem and compared our proposals with the current process. The proposed protocol eliminates the memory exhaustion problem on the client side by using methods for reduction of memory usage.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2481-2490
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• 2015

The issue of PHR is maintained on the server will be in the hospital. PHR information stored on the server, such as a patient's illness and treatment is very sensitive information. Therefore, patients should be guaranteed the protection of privacy. In addition, the PHR should be allowed to group access of it's approach. Therefore, in this paper the proposed group signature using hierarchical identity-based encryption schemes into can guarantee the PHR data privacy. The session key generated by group signature, it is use a tiered approach. The generated session keys safe PHR data transmission is possible. The proposed method is average 80% than the PKI encryption and ID-based encryption rather than average 50% the algorithm processing is more efficient

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.4
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• pp.46-58
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• 2008

Naval combat management system is a kind of complex weapon systems performing naval ship's warfare mission by integrating various types of system including sensor systems, weapon systems and many kinds of communication system. Recently, there are many studies to apply commercial high-level communication middleware to naval combat system development to integrate and interoperate various kinds of heterogeneous on-board systems efficiently. An initial discovery mechanism is required for application modules to start communication with their relevant modules to apply middlware technology in developing naval combat system, which is characterized by large-scale, complex and real-time system. This paper suggests a fast hybrid discovery mechanism which combines static and dynamic discovery mechanism and confirms its adaptability by an experiment on testing environment.

• KIPS Transactions on Computer and Communication Systems
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• v.2 no.9
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• pp.381-392
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• 2013

During the last decade, the multitude of advances attained in terminal computers, along with the introduction of mobile hand-held devices, and the deployment of high speed networks have led to a recent surge of interest in Quality of Service (QoS) for video applications. The main difficulty is that mobile devices experience disparate channel conditions, which results in different rates and patterns of packet loss. One way of making more efficient use of network resources in video services over wireless channels with heterogeneous characteristics to heterogeneous types of mobile device is to use a scalable video coding (SVC). An SVC divides a video stream into a base layer and a single or multiple enhancement layers. We have to ensure that the base layer of the video stream is successfully received and decoded by the subscribers, because it provides the basis for the subsequent decoding of the enhancement layer(s). At the same time, a system should be designed so that the enhancement layer(s) can be successfully decoded by as many users as possible, so that the average QoS is as high as possible. To accommodate these characteristics, we propose an efficient transmission scheme which incorporates SVC-aware dual-channel repetition to improve the perceived quality of services. We repeat the base-layer data over two channels, with different characteristics, to exploit transmission diversity. On the other hand, those channels are utilized to increase the data rate of enhancement layer data. This arrangement reduces service disruption under poor channel conditions by protecting the data that is more important to video decoding. Simulations show that our scheme safeguards the important packets and improves perceived video quality at a mobile device.

• The Transactions of the Korea Information Processing Society
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• v.5 no.4
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• pp.975-983
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• 1998

In these days, information communication systems are based on both open distributed computing technologies and object-oriented techniques like inheritance, encapsulation and object reuse to support various system configuration and application. As information systems are interconnected through unsecure networks, the need for the secure information exchange is more critical than before. In this paper, we have designed and implemented a transparent CORBA-basce Security infrastructure with authentication, security context association, access control and security information management to support a secure applications in distributed object environment. SESAME Ver. 4 was adopted as an external security service to manage user privilege attributes and to distribute keys for data encryption, decryption and integrity. Using filter and transformer with an interface to Object Request Broker, it provides a transparent security service to applications. The filter objects are special classes that allow additional parameters to be inserted into messages before they are sent and removed just after they are received. The transformer objects are special classes that allow direct access to the byte stream of every messages for encryption and decryption before it is sent and just after it is received. This study is to implement the access control interceptor(ACI) and the secure invocation interceptor(SII) of secure ORB defined in CORBA using filter and transformer.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.10
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• pp.2004-2010
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• 2009

The characteristic of the backbond for distribution service in WMNs(Wireless Mesh Networks) is that WMNs has multiple links connected to mesh points and dynamic routing protocol such as AODV to establish routing paths. When the terminal is communicating with the service through new AP, mobile nodes can resume communication by setting only the link between new AP and mobile node in the case of existing WLANs, but WMNs needs path establishment process in multihop networks. Our goal in this paper is to support the seamless communication service by eliminating path establishment delay in WMNs. We present the method that eliminates the handover latency by predicting the location of handover using GPS information and making the paths to their destination in advance. We implement mesh nodes using embedded board that contains proposed handover method and evaluate performance of handover latency. Our experiment shows that handover delay time is decreased from 2.47 to 0.05 seconds and data loss rate is decreased from 20~35% in the existing method to 0~10% level.