• Journal of the Korea Society of Computer and Information
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• v.14 no.5
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• pp.77-83
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• 2009

In this parer, an improved backoff algorithm is proposed by supplementing a multiple of persistence factor for IEEE 802.11 Wireless LAN MAC. This algorithm is proposed to complement the shortcomings of the conventional BEB (Binary Exponential Backoff) algorithm which is used for retransmission to control a new contention window in DCF/EDCF MAC. In channel utilization, collision rate and Goodput viewpoint, we analysis the improved backoff algorithm and compared the result with that of the conventional algorithm In this result, we showed that the performance for PFA backoff algorithm is 10% higher than that for the conventional BEB algorithm when the number of station is 40.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10e
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• pp.289-291
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• 2002

100Mbps의 전송속도를 만족하는 TDMA 방식의 전송 방식의 MAC을 연구중이다. 현재까지 진행된 MAC에 대한 간단한 소개와 또 MAC 프레임의 구조를 설명하고 이를 개발하기 위하여 11Mbps급의 IEEE 802 11b 모뎀을 활용한 방법에 대하여 설명한다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.3
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• pp.1462-1476
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• 2017

The current literature on discrete-time Markov chain (DTMC) based analysis of IEEE 802.15.6 MAC protocols for wireless body area networks (WBANs), do not consider the ACK timeout state, wherein the colliding nodes check the ill fate of their transmissions, while other contending nodes perform backoff check that slot as usual. In this paper, our DTMC model accurately captures the carrier sense multiple access with collision avoidance (CSMA/CA) mechanism of IEEE 802.15.6 medium access control (MAC) and allows the contending nodes performing backoff to utilize the ACK timeout slot during collisions. The compared rigorous results are obtained by considering a non-ideal channel in non-saturation conditions, and CSMA/CA parameters pertaining to UWB PHY of IEEE 802.15.6 MAC protocols.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.14 no.2
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• pp.93-100
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• 2014

IEEE 802.11 Wireless LAN Medium Access Control(MAC) supports two transmission methods, a DCF basic and a RTS/CTS in contention-based access. Even though the RTS/CTS method has been optionally introduced to solve the hidden terminal problem, it is able to produce better performance in some network environments than the basic transmission method. In this paper, the collision probability of wireless channel is mathematically analyzed and applied to measure network throughput using real transmission parameters so that a reference value between throughputs of two methods is obtained. We also confirmed that control signal rates affect overall network throughput and evaluated network throughputs considering collision probability, number of stations, and contention window size of Backoff between two methods respectively.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.301-303
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• 2008

CSMA/CA를 기반으로 하는 IEEE 802.11 무선랜의 MAC에서는 데이터 전송을 제어하기 위한 방법으로 DCF와 PCF를 사용한다. IEEE 802.11 무선랜의 기본적인 액세스 방법으로 사용하는 DCF에서는 스테이션간의 충돌을 줄이기 위해서 임의의 백오프 시간을 각 스테이션의 경쟁윈도우(Contention Window) 범위에서 결정한다. 스테이션은 패킷 전송 후 충돌이 발생하면, 윈도우 크기를 두 배로 증가시키며, 패킷을 성공적으로 전송하면 윈도우 크기를 최소 경쟁 윈도우(Minimum Contention Window)로 감소한다. DCF는 경쟁 스테이션이 적은 상황에서는 비교적 우수한 성능을 보이나 경쟁 스테이션의 수가 많은 경우 처리율, 패킷지연 관점에서 성능이 저하되는 문제점이 있다. 본 논문에서는 IEEE 802.11 MAC 계층 DCF 방식에서의 평균폐기시간에 여러 연구결과들을 비교분석한다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.394-396
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• 2005

IEEE 802.11 MAC은 정지상태 또는 저속 이동중의 사용을 목적으로 개발되었기 때문에 고속의 이동성을 갖는 차량간 통신 환경에서는 성능 개선이 요구된다. 본 논문에서는 차량간 통신에서 802.11 MAC의 성능 분석 및 개선점 도출을 위하여 ns-2 기반 IEEE 802.11g 시뮬레이터를 개발하였으며 차량간 통신 환경에서 RTS/CTS의 효용성을 측정 및 분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.878-884
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• 2013

This paper presents a transmission power control MAC protocol that allows terminals to vary transmit power level on data frame basis in ad hoc network. Unlike the IEEE 802.11 approach, we do not use the RTS/CTS packets to silence the neighboring nodes. Instead, channel gain and distance information between transmitter and receiver terminal are inserted in the RTS/CTS packets. These informations are used to dynamically bound the transmission power. Simulation results indicate that, compared to the GMAC, the proposed MAC protocol achieves a increase in the average frame delivery ratio and a decrease in the average frame delay.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.4
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• pp.793-797
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• 2004

Wireless sensor networks use battery-operated computing and sensing devices. And It can be expected to be deployed in an ad hoc networs. MAC is different from traditional wireless MACs such as IEEE 802.11 in almost every way. so self-configuration and power saving in sensor network are very important goals, while per-node fairness and latency are less important. In this paper, so we use a given prototype for efficient energy conservation to reduce power consumtion that is one of the important character in sensor network and compare energy consumption and collision with IEEE 802.11 MAC. finally we conclude the paper and analyze it.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.182-185
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• 2004

Wireless sensor networks use battery-operated computing and sensing devices. And It can be expected to be deployed in an ad hoc networs. MAC is different from traditional wireless MACs such as IEEE 802.11 in almost every way. so self-configuration and power saving in sensor network are very important goals, while per-node fairness and latency are less important. In this paper, so we use a given prototype for efficient energy conservation to reduce power consumtion that is one of the important character in sensor network and compare energy consumption and collision with IEEE 802.11 MAC. Finally we conclude the paper and analyze it.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2010.10a
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• pp.54-57
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• 2010

Vehicular Ad-hoc Network the core technology of ITS supports safety service or information service to driver and passenger on the roads utilizing V2V and V2I communication. WAVE, the standard of the vehicular ad hoc networks, adopts IEEE 802.11p as MAC protocol and includes the channel coordination algorithm to utilize multiple channels. However, this standard shows the problem related with QoS guarantee of urgent data for driver's safety and the limitation of the performance improvement. In this paper, we introduce WAVE-based Multi-channel MAC protocols that have proposed to resolve above problems and describe their features.