• ETRI Journal
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• v.28 no.6
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• pp.815-818
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• 2006

In the global Internet, a constraint-based routing algorithm performs the function of selecting a routing path while satisfying some given constraints rather than selecting the shortest path based on physical topology. It is necessary for constraint-based routing to disseminate and update link state information. The triggering policy of link state updates significantly affects the volume of update traffic and the quality of services (QoS). In this letter, we propose an adaptive triggering policy based on link-usage statistics in order to reduce the volume of link state update traffic without deterioration of QoS. Also, we evaluate the performance of the proposed policy via simulations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.1
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• pp.323-342
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• 2021

Personal health records (PHRs) is an electronic medical system that enables patients to acquire, manage and share their health data. Nevertheless, data confidentiality and user privacy in PHRs have not been handled completely. As a fine-grained access control over health data, ciphertext-policy attribute-based encryption (CP-ABE) has an ability to guarantee data confidentiality. However, existing CP-ABE solutions for PHRs are facing some new challenges in access control, such as policy privacy disclosure and dynamic policy update. In terms of addressing these problems, we propose a privacy protection and dynamic share system (PPADS) based on CP-ABE for PHRs, which supports full policy hiding and flexible access control. In the system, attribute information of access policy is fully hidden by attribute bloom filter. Moreover, data user produces a transforming key for the PHRs Cloud to change access policy dynamically. Furthermore, relied on security analysis, PPADS is selectively secure under standard model. Finally, the performance comparisons and simulation results demonstrate that PPADS is suitable for PHRs.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.335-345
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• 2017

Recently, location systems using RFID technology have been studied in indoor environments. However, the existing techniques require high computational cost to compute the location of a moving object because they compare the location proximity of all reference tags and objects. In this paper, we propose an RFID based location positioning scheme using event filtering, which reduces the computation cost of calculating the locations of moving objects while maintaining the accuracy of location estimation. In addition, we propose an incremental location update policy to reduce the location update cost for moving objects. We also compare the proposed scheme with one of the localization schemes, LANDMARC using a performance evaluation. As a result, the proposed scheme outperforms LANDMARC in terms of the computational cost of location estimation. The proposed scheme also reduces the cost of location update by using the RFID-based update policy.

• IEMEK Journal of Embedded Systems and Applications
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• v.13 no.5
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• pp.269-277
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• 2018

NAND flash memory has widely been used because of non-volatility, low power consumption and fast access time. However, it suffers from inability to provide update-in-place and the erase cycle is limited. The unit of read/write operation is a page and the unit of erase operation is a block. Moreover erase operation is slower than other operations. We proposed the Adaptive Garbage Collection (called "AGC") policy which focuses on not only reducing garbage collection process time for real-time guarantee but also wear-leveling for a flash memory lifetime. The AGC performs better than Cost-benefit policy and Greedy policy. But the AGC does not consider the operation characteristics. So we proposed the Advanced Adaptive Garbage Collection (called "A-AGC") policy which considers the page write operation count and block erase operation count. The A-AGC reduces the write operations by considering the data update frequency and update data size. Also, it reduces the erase operations by considering the file fragmentation. We implemented the A-AGC policy and measured the performance compared with the AGC policy. Simulation results show that the A-AGC policy performs better than AGC, specially for append operation.

• Proceedings of the Korean Information Science Society Conference
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• 2001.04a
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• pp.217-219
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• 2001

플래쉬 메모리는 데이터 저장 및 변경이 가능한 비휘발성 메모리로 가벼운 무게, 낮은 전력 소모, 충격에 대한 저항성과 빠른 데이터 처리 능력 때문에 이동형 컴퓨터 시스템에서 사용하기에 적당하다. 그러나 플래쉬 메모리는 덮어쓰기(update-in-place)가 불가능하고 각 메모리 셀에 대해 초기화 작업(erasing operation)의 수가 제한되어 있다. 이러한 단점들을 고려하여 세그먼트의 데이터 중 유효 데이터의 비율과 hot 데이터(가까운 시간 안에 update가 될 것이라는 예상되는 data)의 수, 세그멘트가 초기화되었던(easing) 횟수 등을 고려한 새로운 초기화 기법(cleaning policy)을 제안하고자 한다.

• Spatial Information Research
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• v.20 no.5
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• pp.67-76
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• 2012

Recently the mobile DBMS (Database Management System) is popular to store and manage large data in a mobile device. Especially, the research and development about mobile storage structure and querying method for navigation map data in a mobile device have been performed. The performance of the mobile DBMS in which random data accesses are most queries if the NAND flash memory is used as storage media of the DBMS is degraded. The reason is that the performance of flash memory is good in writing sequentially but bad in writing randomly as the features of the NAND flash memory. So, new storage structure and querying policies of the mobile DBMS are needed in the mobile DBMS in which a flash memory is used as storage media. In this paper, we have studied the policy of the database page management to enhance the performance of the frequent random update and applied this policy to the navigation-specialized mobile DBMS which supports incremental map update. And also we have evaluated the performance of this policy by experiments.

• Journal of KIISE:Databases
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• v.37 no.1
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• pp.33-43
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• 2010

In this paper, we propose a new location acquisition scheme based on RFID that reduces the computation cost of location acquisition and keeps the accuracy of the location. In addition, we propose an incremental location update policy to reduce the location update cost for moving objects. To show the superiority of our proposed scheme, we compare it with the existing researches. It is shown through various experiments that the proposed system reduces the computation cost of location estimation 500 times more than existing researches. Also, the proposed system significantly reduces the cost of location update using the RFID-based update policy.

• The Transactions of the Korea Information Processing Society
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• v.7 no.12
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• pp.3964-3975
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• 2000

There are two policies for maintaining consistency among the multiple processor caches in a multiprocessor system: Write invalidate and Write update. In the write invalidate policy, whenever a processor attempt to write its cached block, it has to invalidate all the same copies of the updated block in the system. As a results of this frequent invalidations, this policy results in high cache miss ratio. On the other hand, the write update policy renew them, instead of invalidating all the same copies. This policy has to transfer the updated contents through interconnection network, whether the updated block is ptivate or not. Therefore the network suffer from heavy transaction traffic. In this paper we present an efficient cache coherence protocol for shared memory multiprocessor system connected by slotted ring. This protocol is based on the write update policy, but the updated contents are transferred only in case of updating the shared block. Otherwise, if the updated block is private, the updated contents are not transferred. We analyze the proposed protocol and enforce simulation to compare it with previous version.

• The KIPS Transactions:PartD
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• v.10D no.6
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• pp.917-926
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• 2003

More views in data warehouse, can respond to the users more rapidly because the user's requests may be processed by utilizing only the materialized views with higher probabilities rather than accessing base relations. But, more views cause longer update duration of all the materialized views. During the update time, queries of users can not be processed because accesses to the datawarehouse are blocked. Thus, the update durations of the materialized views are necessary to be reduced. In this paper, we propose algorithm the update duration of the materialized views owing to managing by distinguishing insecton/deletion operations. Though there might overheads for distinguishing insertion/deletion, we concluded that the proposed algorithm could be excellent than others.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.45 no.3
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• pp.78-89
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• 2022

The purpose of this study was to propose useful suggestion by analyzing preventive replacement policy under which there are minor and major failure. Here, major failure is defined as the failure of system which causes the system to stop working, however, the minor failure is defined as the situation in which the system is working but there exists inconvenience for the user to experience the degradation of performance. For this purpose, we formulated an expected cost rate as a function of periodic replacement time and the number of system update cycles. Then, using the probability and differentiation theory, we analyzed the cost rate function to find the optimal points for periodic replacement time and the number of system update cycles. Also, we present a numerical example to show how to apply our model to the real and practical situation in which even under the minor failure, the user of system is not willing to replace or repair the system immediately, instead he/she is willing to defer the repair or replacement until the periodic or preventive replacement time. Optimal preventive replacement timing using two variables, which are periodic replacement time and the number of system update cycles, is provided and the effects of those variables on the cost are analyzed.