• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.11a
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• pp.335-335
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• 2004

• Annual Conference of KIPS
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• 2004.05a
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• pp.1351-1354
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• 2004

기존의 CDMA 1x EV-DO 시스템에서 비실시간 서비스는 Propotional Fairness 알고리즘을 사용해 셀내의 모든 유저에게 fairness를 제공했지만, throughput이 낮았다. 그래서, 이 논문에서는 이를 개선한 cell의 downlink에서 비실시간 서비스를 스케줄링시 fairness를 제공하면서, throughput을 향상시킬 수 있는 방안을 제안하고 구현하였다.

• ETRI Journal
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• v.27 no.1
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• pp.43-52
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• 2005

In this paper, we introduce an adaptive radio resource allocation for IP-based mobile satellite services. We also present a synchronous multibeam CDMA satellite system using an orthogonal resource sharing mechanism among downlink beams for the adaptive packet transmission. The simulation results, using a Ka-band mobile satellite channel and various packet scheduling schemes, show that the proposed system and resource allocation scheme improves the beam throughput by more than two times over conventional systems. The simulation results also show that, in multibeam satellite systems, a system-level adaptation to a user's channel and interference conditions according to user locations and current packet traffic is more efficient in terms of throughput improvement than a user-level adaptation.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.67-69
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• 2004

HR-WPAN(802.15.3)의 CTAP에는 Time Slot(CTA) 할당 스케줄링 기법이 적용되어 있지 않다. 이에 본 논문에서는 CTAP의 채널 할당 방식에 유선망의 패킷 스케줄링방법인 WFQ(Weighted Fair Queuing)를 적용하고자 한다. 현재 표준에서 TDMA를 적용하기 위한 명확한 스케줄링 기법이 없으며, 대량의 트래픽으로 인해 소량의 트래픽이 기아현상을 겪을 수 있는 공정성(Fairness)의 문제가 있다. 따라서 본 논문에서는 각각의 DEV들에 가중치를 적용하여 공정한 방법으로 채널을 할당 받고자 한다. 이를 통해 HR-WPAN의 채널 할당방식에 있어서의 공정성 문제를 해결하고 delay bound를 제공하는 time slot 스케줄링 기법을 제안한다. 본 논문에서는 Weighted Fairness를 적용한 분산적 스케줄링 방법에 대한 연구를 통해 HR-WPAN에서의 성능 향상을 이루고자 한다.

• Journal of information and communication convergence engineering
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• v.16 no.1
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• pp.38-42
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• 2018

In this paper, we consider measurement allocation problem in a spatially correlated sensor field. Our goal is to determine the probability of each sensor's being measured based on its contribution to the estimation reliability; it is desirable that a sensor improving the estimation reliability is measured more frequently. We consider a spatial correlation model of a sensor field reflecting transmission power limit, noise in measurement and transmission channel, and channel attenuation. Then the estimation reliability is defined distortion error between event source and its estimation at sink. Motivated by the correlation nature, we model the measurement allocation problem into a cooperative game, and then quantify each sensor's contribution using Shapley value. Against the intractability in the computation of exact Shapley value, we deploy a randomized method that enables to compute the approximate Shapley value within a reasonable time. Besides, we envisage a measurement scheduling achieving the balance between network lifetime and estimation reliability.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.6B
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• pp.586-592
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• 2002

In this paper, new channel scheduling algorithms which reduce transmission delay caused by wireless network are proposed in AMC/TDM wireless data communication. The concept of the Proposed algorithms is based on the proportional fairness, M-LWDF, and performance-guaranteeing algorithm proposed by Xin Liu. The proposed algorithm can be applied to QoS guaranteeing services as well as best-effort services. Simulation results show that new algorithm reduced transmission delay upto 11.5% in case of proportional fairness algorithm and also decreased transmission delay unto 9% in case of M-LWBF algorithm.

• Journal of information and communication convergence engineering
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• v.8 no.4
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• pp.393-398
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• 2010

For multi-cell environments, coordinated random beamforming technique in multiuser MIMO(multiple-input multiple-output) broadcast channel is considered. In order to mitigate severe interference at receivers, the multi-cell environments might require complex transmitter and receiver design because the scheduler decision based on full channel state information (CSI) in one cell must be intertwined with decision made by other cells' CSI. With limited CSI, however, this paper considers a scheme of randomizing transmitters' beamforming but being coordinated with other cell transmitters. The transmitters in each cell share random beamforming patterns and schedule data transmission within coherent scheduling period. The corandomized beams allow the users to be selected with the highest SINRs even in multi-cell environments. We analyze the performance of the proposed scheme. And numerical results show that the scheme achieves better performance than the conventional random beamforming when applying to multi-cell environments.

• Proceedings of the IEEK Conference
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• 2000.07b
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• pp.735-738
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• 2000

The most important issue in database security is correct concurrency control under the restrictive security policy. The goal of secure transaction management is to keep security and provide many concurrent users with the high availability of database. In this paper, we consider the security environment of multidatabase system with replicated data. The read-from relationship in the existed serializability is improper in security environment. So, we define new read-from relationship and propose new secure 1-copy quasi-seriailzability by utilizing this relationship and display some examples. This security environment requires both the existed local autonomy and the security autonomy as newly defined restriction. To solve covert channel problem is the most difficult issue in developing secure scheduling scheme. The proposed secure 1-copy quasi-serializability is very proper for global transactions in that this serializability not violates security autonomy and prevents covert channel between global transactions.

• Annual Conference of KIPS
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• 2014.04a
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• pp.185-187
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• 2014

멀티채널 무선 센서 네트워크에서 기존의 스케줄링 방법들은 각 노드마다 다른 채널과 타임슬롯을 할당하는 방법을 채택하여 연구하였다. 하지만 여러 채널과 타임슬롯을 사용함으로써 채널가의 간섭, 채널과 타임슬롯의 할당, 채널 변경에 소모되는 에너지와 딜레이 등 추가로 고려해야할 사항들이 발생하였다. 센서 노드는 저전력의 배터리를 사용하기 때문에 효율적인 채널과 타임슬롯 할당 이외에도 채널 변경에 대해 고려되어야 한다. 본 논문에서는 멀티채널 무선센서네트워크 환경에서 최소한의 채널 변경을 지향하는 효율적인 채널과 타임슬롯을 할당하는 방법을 제안한다.

• Annual Conference of KIPS
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• 2013.11a
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• pp.265-267
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• 2013

본 논문에서는 멀티 셀 셀룰러 네트워크에서 채널 환경에 따른 스케줄링 알고리듬의 성능을 평가한다. 무선 통신 환경에서 대표적인 채널모델인 가우시안 채널, 레일리 페이딩 채널, SCME(Spatial Channel Model Extended) 채널 모델에 PF(Proportional Fair)와 MR(Maximum Rate) 스케줄링 기법을 적용했을 때, 시스템 성능을 평가하고 비교한다. 기지국에서 송신된 신호는 채널을 통과하며 변화하고 이는 채널 모델에 따라 달라진다. 채널 모델에 따른 스케줄링 알고리듬 성능 평가 결과 가우시안 채널모델과 레일리 페이딩 채널모델 SCME보다 좋은 성능을 보인다.