• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.05a
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• pp.635-637
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• 2016

센서 네트워크에서 각 센서 노드의 에너지 소모를 최소화하여 에너지 소모를 줄임으로써 망의 지속시간을 늘이는 것이 중요하다. 기존의 MAC(Medium Access Control) 프로토콜은 채널 폴링 기법을 이용하여 효율적인 에너지 관리에 대한 해결책을 제시 하였으나, 그러한 방식에 따른 각 노드의 Duty Cycle이 길어짐으로써 발생하는 에너지 소모에 대한 해결책은 제시하지 못하였다. 본 논문에서는 기존의 채널 폴링과 함께 스케쥴링 알고리즘을 적용하여 Duty Cycle의 주기를 줄임으로써 에너지 소모를 줄인다. 특히 이 방식을 이용하여 멀티홉과 과다한 트래픽에 대한 성능의 평가를 위해 실험을 통해 제안하는 프로토콜의 우수한 성능을 보인다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10c
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• pp.153-155
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• 2000

MCNS의 DOCSIS 규격은 국내외에서 케이블 TV 망을 이용한 HFC 시스템과 무선 링크를 사용하는 BWLL 시스템에서 공유 매체를 통한 데이터 전송 동작 규격으로 사용되고 있다. 기존의 MCNS MAC 프로토콜은 IP 데이터 전송을 위한 Best Effort 서비스 지원하기 위해 설계되었기 때문에 기존 방식으로는 멀티미디어 서비스들을 지원하는데 많은 어려움이 있었다. 이를 해결하기 위해 MCNS에서는 DOCSIS1.1부터 QoS를 지원하기 위한 동작을 추가하였다. 본 논문에서는 새로 규격에 추가된 QoS 관련 서비스 동작 절차와 상향 채널 할달 스케쥴링 방식에 대해 설명하고, 규격에서 정의된 스케쥴링 서비스를 기반으로 각 서비스의 QoS를 지원하기 위한 새로운 할당 알고리즘을 제안하였다. 제안한 알고리즘의 성능을 분석하기 위해 기존의 FCFS 방식의 상향 채널할당 방식과 QoS 지원 상향채널 할당방식의 성능을 시뮬레이션을 통해 비교하였다.

• Journal of Korea Multimedia Society
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• v.12 no.11
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• pp.1521-1529
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• 2009

There is a serious unfairness problem between upstream and downstream flows of AP in IEEE 802.11 Wireless LAN. This problem is because Wireless LAN's DCF MAC protocol provides AP with equal channel access priority to mobile noded. Also, it makes this problem worse that the TCP's Data segment loss is more effective on throughput than the TCP's ACK segment. In this paper, we first make several simulations to analysis the unfairness in the various point of view and to find reasons of the unfairness. Also, this paper presents AP's scheduling scheme to alleviate the unfairness problem and evaluate the scheme through ns2 simulator.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.446-452
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• 2006

In this paper, I evaluated the throughput of various multimedia traffic by using computer simulation over wireless LAN environment based on 802.11e MAC protocol. The number of mobile terminals which generate various traffic and have different Internet QoS varies to improve the reliability of performance evaluation by simulation. Therefore, we investigate throughput of traffic that each mobile terminal generates. I expect that the result of study will be utilized as a fundamental data to control priorities of various types of traffic in case of formulating a scheduling policy supporting a variety of Internet QoS over wired and wireless networks.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.469-472
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• 2014

S-MAC is hybrids of CSMA and TDMA approaches that use local sleep-wake schedules to coordinate packet exchanges and reduce idle listening. In this method, all the nodes are considered with equal priority which may lead to increased delay during heavy traffic. The method introduced in this paper provides high throughput and small end-to-end delay suitable for applications such as real-time voice streaming and its functionality is independent of underlying synchronization protocol. The novel idea behind our scheme is that it uses the priority concept with (m,k)-firm scheduling in order to achieve its objectives. The performance of our scheme is obtained through simulations for various packet sizes, traffic loads which show significant improvements in packet delivery ratio, and delay compared to existing protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.2A
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• pp.55-62
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• 2003

This paper proposes an efficient and differentiated MAC scheduling algorithm for Bluetooth systems. The proposed algorithm guarantees QoS (Quality of Service) requirement of each master-slave pair or application. Conventional MAC scheduling algorithms for Bluetooth take priority of each pair into consideration and demonstrate relatively reasonable performance. However, their performances may depend on traffic characteristic, or they are limited by overheads for signaling. In this paper, we propose a new MAC scheduling algorithm superior to the conventional algorithms from the viewpoints of throughput, delay, and supporting QoS. Our proposed algorithm is evaluated via computer simulations under various environments and compared with the conventional scheduling algorithms. Simulation results indicate that the proposed algorithm shows better performance than the existing algorithms, and can support the QoS demand of each pair.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.7B
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• pp.1229-1238
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• 1999

To maximize the statistical multiplexing gain in wireless ATM MAC, a centralized scheduling function must be provided for the dynamic slot assignment in the wireless ATM access point. Exploiting the dynamic parameters received in the wireless ATM access point, the centralized scheduler will execute a dynamic slot assignment to determine bandwidth required for individual wireless terminal. In this paper, we propose a new scheduling algorithm, which can effectively reduce a burden of the explicit signaling requirement of transmitting the dynamic parameters in a timely manner. We have demonstrated that the proposed approach outperforms the existing schemes in terms of the timeliness of transmitting the dynamic parameters, which is a critical factor to the performance of delay-sensitive service classes, and works as an effective means of dynamic slot assignment without heavily relying on the dynamic parameters in the wireless ATM networks.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.854-857
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• 2008

Wireless sensor consists of an internal power source which has limited life time. Several MAC protocols have exploited scheduled sleep/listen cycles to conserve energy in sensor networks. Duty cycle is a user-adjustable parameter in low duty cycle MAC protocols, which determines the length of the sleep period in a frame. The sire of duty cycle has direct effect on the Performance of MAC Protocols. In this Paper, we simulated TEEM (A Traffic Aware, Energy Efficient MAC) and S-MAC in NS-2 with different duty cycle values and analyze how duty-cycle effects on the performance and energy consumption of both the protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.6A
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• pp.474-480
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• 2005

In this paper, we present a new scheduling scheme for MIMO OFDM Multiuser Diversity System. This scheduling scheme maximizes the system throughput, and at the same time fairly shares the resources based on the feedback information from the receivers and the queue information. To show the effectiveness of the proposed algorithm, we evaluate the performance of the proposed algorithm as compared to K&H and RR algorithms.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.3
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• pp.25-35
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• 2009

인지 무선(CR: Cognitive Radio) 기술은 특정 사용자에게 허가되었으나 일정 시간, 일정 지역에서 사용되지 않는 주파수 대역을 찾아 한시적으로 사용함으로써 주파수 사용 효율을 높이는 기술이다. CR 기술을 사용하는 무선 통신 시스템을 구현하기 위해서는 효과적인 채널 센싱 스케쥴링, 채널 선택, 채널 전환 기법을 제공하는 매체 접근 제어(MAC: Medium Access Control) 프로토콜의 개발이 필수적이다. 이글에서는 CR MAC 프로토콜의 특징과 설계시 고려 사항을 검토하고, 현재까지 제안된 몇 가지 CR MAC 프로토콜을 살펴본다. 이를 통해 최신 연구 동향을 파악하고 향후 연구 과제를 제시한다.