• ETRI Journal
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• v.39 no.1
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• pp.13-20
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• 2017

A method is proposed for scheduling sensor accesses to the shared network in a networked control system. The proposed method determines the access order in which the sensors are granted medium access through minimization of the state estimation error covariance. Solving the problem by evaluating the error covariance for each possible ordered set of sensors is not practical for large systems. Therefore, a convex optimization problem is proposed, which yields approximate yet acceptable results. A state estimator is designed for the augmented system resulting from the incorporation of the optimally chosen communication sequence in the plant dynamics. A car suspension system simulation is conducted to test the proposed method. The results show promising improvement in the state estimation performance by reducing the estimation error norm compared to round-robin scheduling.

• Proceedings of the Korean Information Science Society Conference
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• 2001.10c
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• pp.4-6
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• 2001

본 논문에서는 SAN(Storage Area Network) 기반의 공유파일시스템인 Asphodel 파일 시스템을 이용하여 를러스터 웹 서버를 구성하였다. 그리고 Asphodel 공유 파일 시스템이 가지는 락(lock) 서버를 이용하여 효율적인 웹 분배 정책인 CARD(Cache-Aware Request Dispatch)를 제안하고 이를 설계 구현하였다. 그 결과 후위 서버의 메모리 캐쉬의 적중률을 높임으로써 보통의 분배 정책인 라운드로빈(Round-Robin) 방식에 비해 웹 서버의 throughput과 latency에서의 성능 향상을 보였다.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.3
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• pp.193-204
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• 2006

In most existing distributed Web systems, incoming requests are distributed to servers via Domain Name System (DNS). Although such systems are simple to implement, the address caching mechanism easily results in load unbalancing among servers. Moreover, modification of the DNS is necessary to load considering the server's state. In this paper, we propose a new dynamic load balancing method using dynamic DNS update and round-robin mechanism. The proposed method performs effective load balancing without modification of the DNS. In this method, a server can dynamically be added to or removed from the DNS list according to the server's load. By removing the overloaded server from the DNS list, the response time becomes faster. For dynamic scheduling, we propose a scheduling algorithm that considers the CPU, memory, and network usage. We can select a scheduling policy based on resources usage. The proposed system can easily be managed by a GUI-based management tool. Experiments show that modules implemented in this paper have low impact on the proposed system. Furthermore, experiments show that both the response time and the file transfer rate of the proposed system are faster than those of a pure Round-Robin DNS.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.7A
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• pp.611-619
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• 2005

The present paper proposes two different packet scheduling algorithms in the IEEE 802.16e type TDD-OFDMA downlink, which are the weighted fair scheduling(WFS) and the throughput guarantee scheduling(TGS). The performance of proposed scheduling algorithms are compared to some of conventional schedulers such as round robin(RR), proportional fair(PF), fast fair throughput(FFTH), and fair throughput(FH) in terms of service coverage, effective throughput and fairness at 64 kbps and 128 kbps minimum user throughput requirements. For a relatively smaller throughput(64 kbps) requirement, the proposed algorithms provide higher improvement in the number of users per sector within 95$\%$ service coverage while satisfying the lxEV-DV fairness criterion. For a relatively larger throughput(128 kbps) requirement, the proposed algorithms provide higher coverage enhancement while maintaining the same effective aggregate throughput over PF scheduler.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.10
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• pp.2191-2204
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• 1997

An efficient packet transmit scheduling algorithm should be able to allocate the resource to each connection fairly based on the bandwidth and quality of service requirements negotiated during the call admission procedure and it should be able to isolate the effects of users that are behaving badly. In this paper, we propose an effective round-robin packet transmit scheduling mechanism, which we call the delay tolerant packet reserving scheme (DTPRS) based on delay QoS requirments. The proposed scheme can not only provide fairness and but also reduce delay, delay variation, and packet loss rate by reserving output link time slots of delay tolerant packets and assigning the reserved slotsto delay urgent packets. Our scheme is applicable to high speed networks including ATM network because it only requires O(1) work to process a packet, and is simple enough to implement.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.3
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• pp.22-33
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• 2014

As a standard of WMNs, IEEE 802.11s supports two kinds of MAC algorithm: a mandatory EDCA used by IEEE 802.11e and an optional MCCA. While EDCA classifies traffic according to four Access Categories (AC) and offer differentiated service using a classified priority, MCCA can guarantee the specific bandwidth of users with a TDMA-style bandwidth reservation scheme between mesh routers. In case that a flow is VBR traffic of a multimedia application, MCCA has disadvantage that the reserved bandwidth does not be used entirely, though it guarantees required bandwidth of users and fairness using bandwidth reservation with neighbors' node. In this paper, we showed a problem that is wastes the reserved bandwidth when MCCA is enabled and proposed a new scheduling algorithm to prevent waste of bandwidth and to improve network utilization effectively, named Resource Sharing Round Robin (RSRR) scheduling. Finally we showed simulation results that performance of a proposed RSRR is better than the legacy MCCA through NS-2 simulation.

• Journal of the Korea Society of Computer and Information
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• v.16 no.11
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• pp.45-56
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• 2011

WBAN is short range wireless communication technology which is consists of several small devices close to, attached to or implanted into the human body. WBAN is classified into between medical and non-medical by applications based on technology and medical data with periodic characteristics is used the GTS method for transmitting data to guarantee the QoS. In this paper we proposed algorithm that resolve lack of GTSs while data transmit GTS method in superframe structure of WBAN. Coordinator dynamically allocates GTSs according to the data rate of devices and make devices share GTSs when lack of GTSs. We compared delay bounds, throughput for performance evaluation of the proposed algorithm. In other words, we proposed algorithm adaptive WFQ scheduling that GTS allocation support differential data rate in environments of WBAN. The experiment results show the throughput increased and the maximum delay decreased compared with Round Robin scheduling.

• Journal of the Korean Professional Engineers Association
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• v.34 no.4
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• pp.41-47
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• 2001

The paper describes SR3 (Synchronous Round Robin with Reservations), a collision-free medium access control protocol for all-optical slotted packet networks based on WDM multi-channel ring topologies where nodes are equipped with one fixed-wavelength receiver and one wavelength-tunable transmitter SR3 is derived from the SRR and MMR protocols previously proposed by the same authors for the same class of all-optical networks. SRR and MMR already achieve an efficient exploitation of the available bandwidth, while guaranteeing a throughput-fair access to each node. SR3, In addition, allows nodes to reserve slots. thereby achieving a stronger control on access delays; it is thus well suited to meet tight delay requirements, as it is the case for multimedia applications. Simulation results show that SR3 provides very good performance to guaranteed qualify traffic, but also brings signigicant performance improvements for best-effort traffic. Energy effciency is an important issue for optical network since they must rely on their batteries. We present a novel MAC protocol that achieves a good energy efficiency of optical interface of the network and provides support for diverse traffic types and QoS. The scheduler of the base station is responsible to provide the required QoS to connections on the optical link and to minimise the amount of energy spend by the High speed Network. The main principles of the MaC protocol are to avoid unsuccessful actions, minimise the number of transitions , and synchronise the mobile and the base-station. We will show that considerable amounts of energy can be saved using these principles.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2B
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• pp.107-116
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• 2006

In this paper, we propose a Sensing Resolution-based Grouping(SRG) protocol for wireless sensor networks. SRG is intended for meeting the application's sensing objectives, where sensor nodes are densely deployed and have the determinate accuracy requirement. The primary contribution of this paper is active group header node selection and round-robin procedure, which increase the sensing accuracy and evenly distribute the node energy consumption. The second contribution is use of energy efficient intermediate node selection by considering group size and energy consumption. We present the design principle of SRG and provide simulation results.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.1521-1524
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• 2001

네트워크에서 다양한 애플리케이션의 서비스 성능을 저하시키는 불공정 큐잉 문제를 해결하기 위해 현재 공정 큐잉 분야가 활발히 연구중이다. 그 중에서 DRR(Deficit Round Robin)은 작업 복잡도가 낮고 구현이 간단한 기법으로 이전 라운드에서의 서비스 결손량을 다음 라운드에서 서비스하도록 하여 공정한 서비스를 보장하는 기법이다. 그러나 엔터프라이즈 환경과 같은 고속 네트워크 환경에서 최대 수 kbyte 이상의 패킷 사이즈를 가지는 서비스들에 대해 불필요한 SQ(Service Quantum) 재설정 횟수 및 라운드 순회 횟수로 인한 지연시간 증가를 일으킨다. 본 논문에서는 매 라운드마다 전송을 앞둔 패킷의 사이즈를 고려하여 SQ를 동적으로 설정하는 기법을 제안한다. 제안한 기법은 각 큐의 가장 앞쪽에 있는 패킷들 중 사이즈가 아무리 큰 패킷도 현재 라운드에서 서비스될 수 있고, 패킷을 처리하는데 있어서의 작업 복잡도 또한 최소화하는 기법으로 다양한 애플리케이션들에 대한 지연시간을 최소화한다.