• 전자공학회논문지CI
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• 제48권5호
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• pp.107-116
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• 2011

본 논문에서는 무선 센서 망을 위한 트래픽 적응적 수면시간 기반 매체 접근 제어 (Traffic Adaptive Sleep based Medium Access Control; TAS-MAC) 프로토콜을 제안한다. 제안 된 프로토콜은 클러스터를 구성하는 센서노드에 적용되며 TDMA를 기본 방식으로 사용한다. 기존에 제시된 LEACH와 BMA-MAC과 같은 전형적인 스케줄링 방식을 사용하지만 입력 데이터가 없거나 주변으로부터 발생되는 이벤트 발생이 없는 긴 침묵시간을 고려한다. 이를 위하여 간단한 트래픽 측정기법을 사용하며 기존 중앙집중식 MAC에서 수행하는 불필요한 스케줄링 시간을 줄임으로서 에너지 소모를 적게 한다. 제안된 프로토콜의 프레임은 조사(I), 전송(T), 그리고 수면기간(S)로 구성되며 I-기간 동안 필요한 정보를 수집하여 긴 침묵 시간에 대응한 적당한 수면시간을 동적으로 결정한다. 또한 한 노드에서 클러스터 헤드로 전송할 데이터가 하나 이상일 때, T-기간 동안 다중의 데이터 전송이 가능하도록 TAS-MAC 프로토콜을 개선하여 데이터의 평균 전송 지연을 줄인다. 시뮬레이션을 통하여 에너지 소비와 전송 지연을 분석하고 기존 방식에 비해 에너지 효율이 향상됨을 보인다. 제안된 방식은 에너지 효율이 증가되면서 지연이 상대적으로 증가하는데 에너지 감소 요구를 만족시키는 방안도 논의한다.

• 한국통신학회:학술대회논문집
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• 한국통신학회 2004년도 추계종합학술대회 논문 초록집
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• pp.84-84
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• 2004

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권12호
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• pp.5835-5854
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• 2017

The implementation of IEEE 802.15.6 in Wireless Body Area Network (WBAN) is contention based. Meanwhile, IEEE 802.15.4 MAC provides limited 16 channels in the Superframe structure, making it unfit for N heterogeneous nature of patient's data. Also, the Beacon-enabled Carrier-Sense Multiple Access/Collision-Avoidance (CSMA/CA) scheduling access scheme in WBAN, allocates Contention-free Period (CAP) channels to emergency and non-emergency Biomedical Sensors (BMSs) using contention mechanism, increasing repetition in rounds. This reduces performance of the MAC protocol causing higher data collisions and delay, low data reliability, BMSs packet retransmissions and increased energy consumption. Moreover, it has no traffic differentiation method. This paper proposes a Low-delay Traffic-Aware Medium Access Control (LTA-MAC) protocol to provide sufficient channels with a higher bandwidth, and allocates them individually to non-emergency and emergency data. Also, a Contention Differentiated Adaptive Slot Allocation CSMA-CA (CDASA-CSMA/CA) for scheduling access scheme is proposed to reduce repetition in rounds, and assists in channels allocation to BMSs. Furthermore, an On-demand (OD) slot in the LTA-MAC to resolve the patient's data drops in the CSMA/CA scheme due to exceeding of threshold values in contentions is introduced. Simulation results demonstrate advantages of the proposed schemes over the IEEE 802.15.4 MAC and CSMA/CA scheme in terms of success rate, packet delivery delay, and energy consumption.

• 전자공학회논문지
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• 제52권4호
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• pp.9-16
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• 2015

VANET에서 신속하고 안전한 메시지 전달은 중요한 연구 주제이다. 대부분의 연구가 운전자의 안전성을 높이기 위해 차량 간 주기적인 비콘(Beacon) 브로드캐스트를 가정하고 있다. 본 논문에서는 차량 간 통신에서 이러한 문제점을 해결하고 신뢰성 있는 데이터 전송을 지원하기 위하여 고속으로 이동하는 차량의 주행 환경에 적합한 위치기반 클러스터링을 통한 매체접속제어 프로토콜을 설계하였다. 클러스터 헤드를 통해 각 노드들의 access를 관리하고 자원을 할당함으로써 기존 싱글 채널을 사용하여 경쟁 기반의 MAC 프로토콜에서 발생하는 패킷 충돌 및 통신 지연을 줄이는 것을 시뮬레이션을 통해 확인 하였다.

• Journal of Information Technology Applications and Management
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• 제12권4호
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• pp.13-24
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• 2005

The sensor network is a key component of the ubiquitous computing system which is expected to be widely utilized in logistics control, environment/disaster control, medical/health-care services, digital home and other applications. Nodes in the sensor network are small-sized and exposed to adverse environments. They are demanded to perform their missions with very limited power supply only. Also the sensor network is composed of much more nodes than the wireless ad hoc networks are. In case that some nodes consume up their power capacity, the network topology should change, and rerouting/retransmission is necessitated. Communication protocols studied for conventional wireless networks or ad hoc networks are not suited for the sensor network resultantly. Schemes should be devised to control the efficient usage of node power in the sensor network. This paper proposes a medium access protocol to enhance the efficiency of energy consumption in the sensor network node. Its performance is analyzed by simulation.

• 전자공학회논문지A
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• 제32A권5호
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• pp.42-53
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• 1995

Token bus protocols have been sidely accepted for Medium Access Control (MAC) in real-time networks such as those used in factory automation, distributed process control, nuclear power plant, aircraft and spacecraft. Token bus protocols provide timer-controlled priority mechanism, which offers multiple level of privilege of medium access to different type of traffic. This paper presents and approximate analytical model for the evaluation of variance of waiting time in the time-controlled proiority scheme of token bus protocols. Token bus system is assumed to be operated with singe-service discipline which is the practical case of real-time networks such as those used in distributed process control and factory automations. The approximate analytical model is validated by comparison with the simulation resuls.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 학술대회지
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• pp.681-685
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• 2004

Design of efficient Medium Access Control (MAC) protocols with both high throughput performances is a major focus in distributed contention-based MAC protocol research. In this paper, we propose an efficient contention-based MAC protocol for wireless Local Area Networks, namely, the Developed Collision Resolution (DCR) algorithm. This algorithm is developed based on the following innovative ideas: to speed up the collision resolution, we actively redistribute the backoff timers for all active nodes; to reduce the average number of idle slots, we use smaller contention window sizes for nodes with successful packet transmissions and reduce the backoff timers exponentially fast when a fixed number of consecutive idle slots are detected. We show that the proposed DCR algorithm provides high throughput performance and low latency in wireless LANs.

• Journal of Information Processing Systems
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• 제4권2호
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• pp.41-52
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• 2008

In this paper, we discuss a novel reservation-based, asynchronous MAC protocol called 'Multi-rate Multi-hop MAC Protocol' (MMMP) for multi-hop ad hoc networks that provides QoS guarantees for multimedia traffic. MMMP achieves this by providing service differentiation for multirate real-time traffic (both constant and variable bit rate traffic) and guaranteeing a bounded end-to-end delay for the same while still catering to the throughput requirements of non real time traffic. In addition, it administers bandwidth preservation via a feature called 'Smart Drop' and implements efficient bandwidth usage through a mechanism called 'Release Bandwidth'. Simulation results on the QualNet simulator indicate that MMMP outperforms IEEE 802.11 on all performance metrics and can efficiently handle a large range of traffic intensity. It also outperforms other similar state-of-the-art MAC protocols.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.425-426
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• 2008

본 논문에서 설계한 802.11 MAC(Medium Access Control)은 하드웨어와 소프트웨어의 통합 구조로 되어 있다. MAC에서 가장 빠르게 동작해야 하는 프레임 전송과 수신블록은 하드웨어로 설계를 하였고, 그 외에는 소프트웨어로 설계가 되었다. 하드웨어로 설계된 MAC은 802.11 표준문서에 포함된 SDL(Specification and Description Language)을 기초하여 설계하였으며, 성능 향상을 위하여 수신블록의 중복 프레임 검사를 수행하는 블록과 프레임을 분석하여 정보를 추출하는 블록을 SDL과 다르게 설계 하였다. 삼성 0.35공정 라이브러리를 이용하여 합성한 결과 3만 게이트의 크기를 갖으며, 최대 동작 주파수는 100MHz이다. 메모리는 47Kbits SRAM을 사용하였다. 실제동작의 검증에 앞서 Mentor Graphics사의 ModelSim을 이용하여 시뮬레이션을 수행하였으며, 동작 검증은 Huins 사의 Altera Excalibur FPGA가 탑재된 XP8000 보드를 이용하여 이루어 졌다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권5호
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• pp.1267-1285
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• 2012

Wireless Body Area Networks (WBANs) deal with variety of healthcare services with diverse Quality of Service (QoS) requirements. However, QoS handling is a challenging problem in such networks. In general, QoS related problems can be addressed from different layers in the networking protocol suite. Design of an efficient QoS aware Medium Access Control (MAC) protocol can address this problem in MAC layer. This paper analyzes the QoS requirements of WBAN, identifies the requisites of QoS handling system, and outlines the trends that are being followed for its advancement with focus on QoS issues at MAC layer. We review some prior works, compare them, and analyze the current research concerned with problem of providing QoS in WBAN. We also explore some open issues and discuss them.