• Journal of KIISE:Information Networking
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• v.27 no.1
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• pp.1-11
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• 2000

Recently, the explosive popularity of Internet gave birth to researches on Distributed Virtual Environments(DVE). They aim at providing a shared application data environment at realtime for users participating in the same application session across Internet. As more users join the session, and as more multimedia data are shared, because of network resource limitation, it is more difficult to maintain the quality of DVE, such as users' satisfaction level. Previous works mainly tried to solve the scalability, synchronization and data transport issues at the application level, with limited success. We suggest a new network centric solution, that consists of a novel network architecture and protocols upon which any large-scale DVE application can be easily developed. The performance of the proposed scheme, called GAIA, is verified by simulation.

• The Journal of the Korea Contents Association
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• v.7 no.10
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• pp.1-9
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• 2007

Allocation and management of the resource is very important in wireless networks because the wireless resource is limited. Therefore, the importance of designing cross layer, which adapt between different layers, is on the rise. In this paper, we investigate the scheduling techniques of the cross layer. This paper researches conventional scheduling methods and proposes the complementary scheduling method. On multimedia environment, the scheduling method must be applied variably because of offering variable services. Therefore, this paper proposes the new scheduling method according to the variable services. The proposed method shows that utility efficiency of the wireless resource more excellent than the conventional method through the simulations.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.261-269
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• 2023

We propose to design a Holochain-based security and privacy protection system for resource-constrained IoT healthcare systems. Through analysis and performance evaluation, the proposed system confirmed that these characteristics operate effectively in the IoT healthcare environment. The system proposed in this paper consists of four main layers aimed at secure collection, transmission, storage, and processing of important medical data in IoT healthcare environments. The first PERCEPTION layer consists of various IoT devices, such as wearable devices, sensors, and other medical devices. These devices collect patient health data and pass it on to the network layer. The second network connectivity layer assigns an IP address to the collected data and ensures that the data is transmitted reliably over the network. Transmission takes place via standardized protocols, which ensures data reliability and availability. The third distributed cloud layer is a distributed data storage based on Holochain that stores important medical information collected from resource-limited IoT devices. This layer manages data integrity and access control, and allows users to share data securely. Finally, the fourth application layer provides useful information and services to end users, patients and healthcare professionals. The structuring and presentation of data and interaction between applications are managed at this layer. This structure aims to provide security, privacy, and resource efficiency suitable for IoT healthcare systems, in contrast to traditional centralized or blockchain-based systems. We design and propose a Holochain-based security and privacy protection system through a better IoT healthcare system.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.87-96
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• 2020

The multi function radar is searching target and tracking through resource management at the same time. Increasing resource allotment of track, if more targets and faster the renewal rate of track, lead to decreasing quota of searching resource in limited resource. When the resource of search are decreased, it becomes degrade searching performance such as revisit time, number of detecting chance and tracking etc. Degraded performance of search reduces guided missile defense probability in complex strategy such as ship self defense. In this paper, we developed a modeling and simulation (M&S) tool that uses own-ship model, radar model, target model and defense model for analysis of self defense in complex strategy. We analyzed influence of ship self defense in complex strategy according to various target environments and track performance.

• ETRI Journal
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• v.25 no.3
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• pp.179-186
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• 2003

Using biometrics to verify a person's identity has several advantages over the present practices of personal identification numbers (PINs) and passwords. At the same time, improvements in VLSI technology have recently led to the introduction of smart cards with 32-bit RISC processors. To gain maximum security in verification systems using biometrics, verification as well as storage of the biometric pattern must be done in the smart card. However, because of the limited resources (processing power and memory space) of the smart card, integrating biometrics into it is still an open challenge. In this paper, we propose a fingerprint verification algorithm using a multi-resolution accumulator array that can be executed in restricted environments such as the smart card. We first evaluate both the number of instructions executed and the memory requirement for each step of a typical fingerprint verification algorithm. We then develop a memory-efficient algorithm for the most memory-consuming step (alignment) using a multi-resolution accumulator array. Our experimental results show that the proposed algorithm can reduce the required memory space by a factor of 40 and can be executed in real time in resource-constrained environments without significantly degrading accuracy.

• Journal of Korean Society of Water and Wastewater
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• v.33 no.4
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• pp.291-297
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• 2019

Phosphorus is a vital resource for sustaining agriculture and nutrition, but a limited non-renewable resource. Thus, the recovery of phosphorus from waste activated sludge(WAS) was attempted by microwave heating and magnesium ammonium phosphorus(MAP) crystallization. Polyphosphate-accumulating organisms(PAOs) in WAS release phosphate from the cell when they are exposed to high temperature environments. Microwave heating caused phosphorus and ammonia to release from WAS. The amount was increased with increasing temperature, showing that 88.5% of polyphosphate present in the cells were released in the form of phosphate at $80^{\circ}C$. A similar result was also observed in the release of ammonia. On the other hand, both phosphorus and ammonia were crystallized with magnesium, and then was harvested as MAP. Phosphorus recovery rate reached almost 97.8%, but the ammonia was about 13.4%. These results cleary indicate that phosphorus could be recovered from WAS using a physiological trait of PAOs. Heavy metal analyses also show that the MAP crystal is useful and safe as a phosphorus fertilizer.

• The Journal of Korean Association of Computer Education
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• v.11 no.5
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• pp.67-76
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• 2008

Grid computing has a large scale virtual computing environment that enables a collaborative processing through sharing resources of geographically distributed organizations. In recent year, the development of wireless networks and mobile devices enables mobile devices to consider as a resource of the grids. However, there are some problems such as low performance of processors, small capacity of storages, limited capacity of battery, and low bandwidth. In this paper, to overcome these limitations occurred in mobile grid environments, we proposed a proxy-based mobile grid system. Our proposed system enables mobile devices to play roles as a resource consumer and a resource provider and to collaborate with wired grids through a mobile router. Also, we propose an adaptive job scheduling scheme to cope with context changes of mobile devices and compare our scheduling scheme with other scheduling schemes using a simulation tool, SimGrid, to verify the validity of our job scheduling scheme.

• KIISE Transactions on Computing Practices
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• v.20 no.12
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• pp.688-693
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• 2014

With the advent of ubiquitous environments, the smart phone has come into wide use and the demand for various content increases. Thus, in order to efficiently utilize limited resources cognitive radio technology is regarded as a possible solution. Besides spectrum sensing or access schemes, the provision of VoIP traffic service for secondary users with limited spectrum resources is a very important issue. In this paper, a resource allocation and control system for VoIP QoS provision in cognitive radio networks is proposed. Firstly, as the system model, the time structure of the network is addressed and, according to the structure, a bandwidth broker is proposed. In addition, based on available bandwidth estimated by the bandwidth broker, a connection admission control for secondary users is developed. It is demonstrated that the provision of VoIP QoS is greatly affected by channel utilization, the number of channels, and the length of timeslot.

• Journal of information and communication convergence engineering
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• v.10 no.1
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• pp.21-26
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• 2012

As the new requirements for wireless sensor networks are emerging, real-time communications is becoming a major research challenge because resource-constrained sensor nodes are not powerful enough to accommodate the complexity of the protocol. In addition, an efficient energy management scheme has naturally been a concern in wireless sensor networks for a long time. However, the existing schemes are limited to meeting one of these two requirements. To address the two factors together, we propose real-time communications with two approaches, a protocol for satisfied conditions and one for unsatisfied. Under the satisfied requirement, existing real-time protocol is employed. On the other hand, for the unsatisfied requirement, the newly developed scheme replaces the existing scheme by adjusting the transmission range of some surplus nodes. By expanding the transmission range, the end-to-end delay is shortened because the number of intermediate nodes decreases. These nodes conserve their energy for real-time communications by avoiding other activities such as sensing, forwarding, and computing. Finally, simulation results are given to demonstrate the feasibility of the proposed scheme in high traffic environments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.5B
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• pp.833-839
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• 2010

Mobility of sensor node is one of the rising issues in Wireless Sensor Networks (WSN). However, current security researches on WSN only consider static environments. Thus they are not sufficient to be deployed in the dynamic environment where the resource is limited. In this paper, we propose the efficient node authentication and key exchange protocol that reduces the overhead in node re-authentication.