• ETRI Journal
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• 제42권2호
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• pp.175-185
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• 2020

Inter-cell interference (ICI) is a major problem in heterogeneous networks, such as two-tier femtocell (FC) networks, because it leads to poor cell-edge throughput and system capacity. Dynamic ICI coordination (ICIC) schemes, which do not require prior frequency planning, must be employed for interference avoidance in such networks. In contrast to existing dynamic ICIC schemes that focus on homogeneous network scenarios, we propose a novel semi-distributed dynamic ICIC scheme to mitigate interference in heterogeneous network scenarios. With the goal of maximizing the utility of individual users, two separate algorithms, namely the FC base station (FBS)-level algorithm and FC management system (FMS)-level algorithm, are employed to restrict resource usage by dominant interference-creating cells. The distributed functionality of the FBS-level algorithm and low computational complexity of the FMS-level algorithm are the main advantages of the proposed scheme. Simulation results demonstrate improvement in cell-edge performance with no impact on system capacity or user fairness, which confirms the effectiveness of the proposed scheme compared to static and semi-static ICIC schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권1호
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• pp.186-205
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• 2019

Intercell interference coordination (ICIC) is considered as a promising technique to increase the spectral efficiency of OFDMA cellular systems. The soft frequency reuse (SFR) and fractional frequency reuse (FFR) are representative and efficient management techniques for ICIC. Herein, to enhance the performance of the SFR scheme, we propose a call admission (CAC) scheme. In this CAC scheme, called Spectrum handoff-SFR(S-SFR), the spectrum handoff technique is applied to the user equipment (UE) located near the cell center. We derive the traffic analysis model to describe the S-SFR. In addition, a two-dimensional (2-D) Markov chain and an outage analysis are used in our analytical model. From the traffic analysis, the significant performance measures are the outage probability, call blocking probability, system throughput and resource utilization. Based on those, the outage probability and system throughput are obtained using resource utilization as an interference pattern. The analytical results are verified with computer simulation results. Finally, we compare our proposed scheme with other ICI schemes.

• 한국통신학회논문지
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• 제28권9B호
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• pp.793-805
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• 2003

헤더 정보와 버스트를 분리하여 전송되는 광 버스트 스위칭 망에서 장애의 발생은 심각한 서비스 품질 저하를 초래할 수 있으므로 신속한 복구 대책을 수립하여 망에서 발생하는 장애의 영향을 최소화하여야 한다. 본 논문에서는 먼저 기존에 제안된 복구 기법을 광 버스트 스위칭 망에 적용하여 각 링크의 장애에 따른 망 이용률 분석 및 버스트 손실률 등을 비교 평가하였다. 이에 대한 격과를 고려하여 망 구성 형태와 장애 링크의 위치를 고려한 ASPR (Area border router Sub-Path Restoration) 기법을 제안하였다. 제안된 기법은 장애 복구 지연 시간과 파장 변환기의 사용 효율성 관점에서 좋은 성능을 보이며 버스트 손실률, 망 자원 이용률, 그리고 버스트 처리율 관점에서 다른 기법과 비교 평가하였다.

• Journal of Communications and Networks
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• 제15권6호
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• pp.614-634
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• 2013

The proliferation of real-time multimedia services requires huge amounts of data transactions demanding strict quality-of-service (QoS) guarantees. Multicast transmission is a promising technique because of its efficient network resource utilization. However, high head-of-line (HOL) blocking probability and lack of service-specific QoS control should be addressed for practical implementations of multicast networks. In this paper, a topology aware fanout set division (TAFD) scheme is proposed to resolve these problems. The proposed scheme is composed of two techniques that reduce HOL blocking probability and expedite packet delivery for large-delay branches regarding multicast tree topology. Since management of global topology information is not necessary, scalability of the proposed scheme is guaranteed. Mathematical analysis investigates effects of the proposed scheme and derives optimal operational parameters. The evaluation results show that the TAFD scheme achieves significant delay reduction and satisfies required delay bounds on various multicast networks.

• Asia pacific journal of information systems
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• 제7권1호
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• pp.85-97
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• 1997

This paper is concerned with knowledge representation schemes best suited for human resource management (HRM) problem domains including human resource planing, selection, placement, compensations, performance evaluation, training and labor-management relations. In order to suggest the scheme we consider two research gods. First, we evaluate and prioritize. The knowledge representation techniques of frames rules, semantic nets and predicate logic that hove been recommended to managerial domains. The combined Analytic Hierarchy Process technique is employed to combine individual judgments effectively between two different expert groups. As a result if we are to select a single knowledge representation technique, a frame representation is best for most HRM domains and to combine frames with others is another choice. Second as a strategy for knowledge representation schemes we show some examples for each damn in terms of labeled semantic nets and two types of rules derived from the semantic nets. We propose nine knowledge components as ontologies. The labeled semantic nets con provide some benefits compared with conventional one. More clearly definea node rode information maces it easy to find the ac information. In the rule sets, the variables are the node of the semantic nets. The consistency of rules is validated by the relationship of the knowledge components.

• 한국경영과학회:학술대회논문집
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• 대한산업공학회/한국경영과학회 2000년도 춘계공동학술대회 논문집
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• pp.160-163
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• 2000

Due to the complexities of the real-world system, a water resource management program has to deal with various types of data. It appears that management personnel who has to use the program usually suffers from the technical burdens of handling large amount of data and understanding the optimization theory when they try to interpret the results. By combining the capabilities of database technology and modeling technique with optimization procedure we can develop a reliable decision supporting tool for multi-reservoir operation planning, which yields operating schedule for each dam in a river basin. We introduce two special data handling methodology for the real world application. First, by treating dams, hydro-electric power generating facilities and demand sites as separate database tables, the proposed data handling scheme can be applied to general water resource system in Korea. Second, by assigning variable names using predetermined key words, we can save searching time for identifying the moaning of the variables, so that we can quickly save the results of the optimization run to the database.

• 한국통신학회논문지
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• 제40권12호
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• pp.2410-2418
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• 2015

In this paper, we consider the femto users and their mutual interference as graph elements, nodes and weighted edges, respectively. The total bandwidth is divided into a number of resource blocks (RBs) and these are assigned to the femto user equipment (FUEs) using a graph coloring algorithm. In addition, resources blocks are assigned to the femto users to avoid inter-cell interference. The proposed scheme is compared with the traditional scheduling schemes in terms of throughput and fairness and performance improvement is achieved by exploiting the graph coloring scheme.

• 대한산업공학회지
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• 제34권4호
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• pp.445-459
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• 2008

This paper addresses a call admission control(CAC) scheme giving handoff calls a priority over new calls for OFDMA wireless communication systems. The characteristics of OFDMA system and a variety of user QoS (Quality of Service) requirements are incorporated into the proposed CAC scheme which consists of several optimization modules for the system resource(subcarriers and power) allocations. The mathematical models and its solution methods for the embedded resource allocation problems are proposed. Some extensive computational experiments are conducted to illustrate the superiority of our CAC.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권8호
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• pp.2042-2060
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• 2013

In wireless sensor networks (WSNs), energy efficiency is one of the most essential design considerations, since sensor nodes are resource constrained. Group communication can reduce WSNs communication overhead by sending a message to multiple nodes in one packet. In this paper, in order to simultaneously resolve the transmission security and scalability in WSNs group communications, we propose a hierarchical cluster-based secure and scalable group key management scheme, called HRKT, based on logic key tree and route key tree structure. The HRKT scheme divides the group key into cluster head key and cluster key. The cluster head generates a route key tree according to the route topology of the cluster. This hierarchical key structure facilitates local secure communications taking advantage of the fact that the nodes at a contiguous place usually communicate with each other more frequently. In HRKT scheme, the key updates are confined in a cluster, so the cost of the key updates is reduced efficiently, especially in the case of massive membership changes. The security analysis shows that the HRKT scheme meets the requirements of group communication. In addition, performance simulation results also demonstrate its efficiency in terms of low storage and flexibility when membership changes massively.

• 한국멀티미디어학회논문지
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• 제11권10호
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• pp.1409-1419
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• 2008

P2P 네트워크가 가진 오픈성과 익명성 때문에 P2P 참여자들은 손쉽게 신뢰할 수 없는 자원들을 확산할 수 있다. 신뢰할 수 없는 자원의 확산을 감소시킴과 동시에 이러한 자원을 제공하는 악의적인 피어들이 P2P 네트워크에 참여하는 것을 제한하기 위하여 피어들의 과거 행동을 나타내는 평판을 이용할 수 있으며 이 정보는 피어들의 미래 행동을 예측하는데 도움이 된다. 한편 평판을 참조하는데 있어 몇몇 피어는 특정 피어의 평판을 증가 또는 감소시키기 위하여 고의적으로 거짓 평가(false feedback)를 제공할 수 있다. 이에 본 논문에서는 거짓 평가를 주는 피어들을 식별함으로써 P2P 네트워크의 신뢰성과 효율성을 향상시킬 수 있는 새로운 평판 관리 기법, TrustRRep(Trustable Resource sharing service using Reputation)를 제안하고자 한다. 제안기법은 악의적인 피어들에 의한 자원 공유를 식별함으로써 공유 자원에 대한 신뢰성 또한 제공할 수 있다. 본 논문에서는 NS-2 시뮬레이터를 이용하여 제안 기법과 기존 평판 관리 기법의 효율성을 비교하고 분석하였다. 제안 기법은 신뢰할 수 없는 자원에 대한 다운로드 횟수를 감소시켜 신뢰할 수 없는 자원의 확산을 막고, 거짓 평가를 주는 피어의 식별 및 피어들의 평판에 신뢰성을 제공한다. 또한 악의적인 피어들의 신뢰 값을 감소시킴으로써 P2P 네트워크의 참석에 제약을 가한다.