• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2004년도 정기총회 및 학술대회
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• pp.291-294
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• 2004

Wireless sensor network을 위 한 MAC(Medium Access Control) layer를 low-rate WPAN을 목적으로 한 IEEE 802.15.4 사양에 따라 구현하고 검증하였다. 센서 네트워크의 노드는 배터리로 동작하므로 에너지 소모가 가장 큰 걸림돌이 된다. power saving을 위한 몇 가지 방법을 포함한 IEEE 802.15.4 MAC protocol을 구현함으로써 wireless sensor network에 적용 가능함을 보였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권2호
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• pp.764-784
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• 2017

Energy efficiency is an essential requirement in designing a MAC protocol for wireless sensor networks (WSNs) using battery-operated sensor nodes. We proposed a new receiver-initiated MAC protocol, RIX-MAC, based on the X-MAX protocol with asynchronous duty cycles. In this paper, we analyzed the performance of RIX-MAC protocol in terms of throughput, delay, and energy consumption using the model. For modeling the protocol, we used the Markov chain model, derived the transmission and state probabilities, and obtained the equations to solve the performance of throughput, delay, and energy consumption. Our proposed model and analysis are validated by comparing numerical results obtained from the model, with simulation results using NS-2.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제9권5호
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• pp.1733-1751
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• 2015

The IEEE 802.15.4 standard not only provides a maximum of seven guaranteed time slots (GTSs) for allocation within a superframe to support time-critical traffic, but also achieves ultralow complexity, cost, and power in low-rate and short-distance wireless personal area networks (WPANs). Real-time wireless body area sensor networks (WBASNs), as a special purpose WPAN, can perfectly use the IEEE 802. 15. 4 standard for its wireless connection. In this paper, we propose an adaptive GTS allocation scheme for real-time WBASN data transmissions with different priorities in consideration of low latency, fairness, and bandwidth utilization. The proposed GTS allocation scheme combines a weight-based priority assignment algorithm with an innovative starvation avoidance scheme. Simulation results show that the proposed method significantly outperforms the existing GTS implementation for the traditional IEEE 802.15.4 in terms of average delay, contention free period bandwidth utilization, and fairness.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권5호
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• pp.1604-1617
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• 2014

This paper proposes RIX-MAC (Receiver-Initiated X-MAC), a new energy-efficient MAC protocol based on an asynchronous duty cycling. RIX-MAC improves energy efficiency through utilizing short preambles and adopting the receiver-initiated approach, where RIX-MAC minimizes sender nodes' energy consumption by enabling transmitters to predict receiver nodes' wake-up times. It also reduces receiver nodes' energy consumption by decreasing the number of control frames. We use the network simulator to evaluate RIX-MAC's performance. Compared to the prior asynchronous duty cycling approaches of X-MAC and PW-MAC, the proposed protocol shows a remarkable improvement in energy-efficiency and end-to-end delay.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제8권6호
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• pp.1901-1913
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• 2014

The IEEE 802.15.6 is a communication standard for Wireless Body Area Networks (WBANs). This standard includes a prioritized slotted Aloha as a choice for medium access control. This protocol is different from the traditional version as it has integral considerations for certain priorities of users. It attempts to resolve collision by halving the probability of retransmission, lower bounded by to a minimum, in the alternate slots to follow. In this paper, we present an analytical model to compute the non-saturated throughput of this protocol in the presence of finite number of nodes. The model is validated against simulation.

• Journal of Communications and Networks
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• 제14권6호
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• pp.710-718
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• 2012

The implementation of a common control channel is one of the most challenging issues in cognitive radio networks, since a fully reliable control channel cannot be created without reserving bandwidth specifically for this purpose. In this paper, we investigate a promising solution that exploits the ultra wide band (UWB) technology to let cognitive radio nodes discover each other and exchange control information for establishing a communication link. The contribution of this paper is threefold: (i) We define the communication protocol needed to let cognitive radio nodes discover each other and exchange control information for link set up, (ii) we overcome the gap in coverage, which typically exists between UWB and long-medium range technologies, by using multi-hop communication, (iii) we evaluate the performance of our approach by adopting an accurate channel model and show its benefits with respect to an in-band signaling solution.

• Journal of Communications and Networks
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• 제11권5호
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• pp.489-499
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• 2009

We describe the fundamental issue of scheduling the allocation of wireless network resources and provide several formulations of the associated problems. The emphasis is on scheduling transmission attempts. We place this problem in the context of existing approaches, like information theoretic and traditional network theoretic ones, as well as novel avenues that open up the possibility of addressing this issue for non-stationary and non-ergodic environments. We summarize concrete recent results for specific special cases that include unicast and multicast traffic, different objective functions, and reduced complexity versions of the problem. We conclude with some thoughts for future work. We identify and single out the cross-layer nature of the problem and include a simple physical-layer criterion in what is mostly a medium access control (MAC) problem.

• 자연과학논문집
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• 제8권2호
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• pp.93-99
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• 1996

이 연구에서는 음성과 데이터가 통합된 트래픽에 대하여 Expressnet과 FDDI의 성능을 비교하였다. 모든 시뮬레이션 결과에서 FDDI가 더 많은 음성 스테이션을 지원하는 것으로 나타났다. Expressnet에 비하여, FDDI가 파일전송형 데이타 트래픽에 대하여 높은 throughput을 보였으나 대화형 트래픽에 대해서는 긴 지연 시간을 보였다.

• ETRI Journal
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• 제37권6호
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• pp.1096-1107
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• 2015

This paper presents a dynamic retry adaptation scheme for H.264 HD video, called DRAS.264, which dynamically adjusts the retry limits of frames at the medium access control (MAC) layer according to the impact those frames have on the streamed H.264 HD video. DRAS.264 is further improved with a bandwidth estimation technique, better prediction of packet delays, and expanded results covering multi-slice video. Our study is performed using the Open Evaluation Framework for Video Over Networks as a simulation environment for various congestion scenarios. Results show improvements in average peak signal-to-noise ratios of up to 4.45 dB for DRAS.264 in comparison to the default MAC layer operation. Furthermore, the ability of DRAS.264 to prioritize data of H.264 bitstreams reduces error propagation during video playback, leading to noticeable visual improvements.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 통신소사이어티 추계학술대회논문집
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• pp.269-272
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• 2003

Ad hoc 네트워크에 대한 상업적인 관심이 지속적으로 증가함에 따라, 최근 Ad hoc 네트워크에 QoS (Quality of Service)를 지원하기 위한 많은 연구가 이루어지고 있다. 지금까지의 연구는 대부분 QoS 기반 라우팅 프로토콜과 자원 예약 (resource reservation) 그리고 QoS MAC (Medium Access Control) 프로토콜에 관한 것이었다. Ad hoc 네트워크에 QoS를 제공하기 위해서는 위의 요소들이 상호 협력하여 동작하고 Ad hoc 네트워크의 특성이 충분히 고려된 005 모델에 관한 연구가 절실히 필요하다. 본 논문에서는 Ad hoc 네트워크에서 종단 사용자간 (end-to-end) 005를 제공하기 위한 서비스 모델의 설계와 구현방법에 대해 제안하였다.