• Journal of Communications and Networks
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• 제17권3호
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• pp.275-285
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• 2015

To improve the efficiency of carrier sense multiple access (CSMA)-based medium access control (MAC) protocols, CSMA with collision resolution (CSMA/CR) has been proposed. In the CSMA/CR, a transmitting station can detect a collision by employing additional sensing after the start of a data transmission and then resolve the next collision that might occur by broadcasting a jam signal during a collision detection (CD) period. In this paper, we analyze the delay of a CSMA/CR based on a generic p- persistent CSMA model and obtain the minimum achievable delay of the CSMA/CR by finding the optimal length of the CD period according to the number of contending stations. Through this delay analysis, we also investigate the throughput-delay characteristics of the CSMA/CR protocol according to various parameters. Analysis and simulation results show that the CSMA/CR has a considerably lower delay and its throughput-delay characteristic is significantly improved than the conventional CSMA/CA and wireless CSMA/CD protocols.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권3호
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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.

• 한국통신학회논문지
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• 제32권9B호
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• pp.598-603
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• 2007

본 논문에서는 무선센서 네트워크에서 서비스의 질(QoS)을 지원하면서 전송 효율을 높이기 위한 무선 센서네트워크에서의 QMAC 프로토콜을 제안한다. 제안된 QMAC에서는 우선순위를 가지는 패킷 전송을 원하는 송신노드가 CSMA/CA 방식을 통하여 수신 노드에게 전송 요청을 하고, 수신 노드에서는 네트워크 토폴로지와 전송되어지는 패킷의 우선순위와 전송 트래픽 양에 따라 TDMA 방식으로 적절히 슬롯을 할당함으로 여러 수신 노드들 사이에 슬롯 중복 할당으로 인한 충돌을 낮춤으로 QoS를 지원하면서 동시에 전송효율을 높일 수 있다는 장점을 가진다.

• International journal of advanced smart convergence
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• 제1권1호
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• pp.14-18
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• 2012

This paper presents a fair MAC protocol based on the CSMA/CA algorithm in visible light communication (VLC) networks. The problem of bandwidth sharing among differentiated priority in VLC networks can be solved by using number of backoff time and backoff exponent parameters with AIFS. The proposed algorithm can achieve fair allocation of the bandwidth resource among differentiated priority. The two dimension Markov chain is assisted for analyzing the proposed mechanism about throughput and delay metrics. Numerical results show that our proposed algorithm improves the fairness among different traffic flows.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 심포지엄 논문집 정보 및 제어부문
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• pp.321-323
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• 2006

The IEEE 802.15.4 uses a CSMA/CA algorithm on access of media. The CSMA/CA algorithm does Random Backoff before the data is transmitted to avoid collisions. The random backoff is a kind of unavoidable delays and introduces the side effect of energy consumptions. To cope with those problems we propose a new media access algorithm, the Priority Based Ordered Media Access (PBOMA) algorithm, which uses different IFSs. The PBOMA algorithm uses Sampling Rate and Beacon Interval to get a different access probability(or IFS). The access probability is higher, the IFS is shorter. Note that The transfer of urgent data uses tone signal to transmit it immediately. The proposed algorithm is expected to reduce the energy consumptions and the delay.

• Journal of Information Processing Systems
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• 제16권5호
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• pp.1048-1063
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• 2020

In this study, we propose a reinforcement learning agent to control the data transmission rates of nodes in carrier sensing multiple access with collision avoidance (CSMA/CA)-based wireless networks. We design a reinforcement learning (RL) agent, based on Q-learning. The agent learns the environment using the timeout events of packets, which are locally available in data sending nodes. The agent selects actions to control the data transmission rates of nodes that adjust the modulation and coding scheme (MCS) levels of the data packets to utilize the available bandwidth in dynamically changing channel conditions effectively. We use the ns3-gym framework to simulate RL and investigate the effects of the parameters of Q-learning on the performance of the RL agent. The simulation results indicate that the proposed RL agent adequately adjusts the MCS levels according to the changes in the network, and achieves a high throughput comparable to those of the existing data transmission rate adaptation schemes such as Minstrel.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2017년도 추계학술발표대회
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• pp.131-132
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• 2017

CSMA/CA 기반 무선 네트워크에서 장치들은 패킷 충돌을 회피하기 위해 무선 채널을 타 장치가 사용 중인 것을 감지하면 데이터를 전송하지 않고 대기 (Backoff) 한다. 이 Backoff는 Contention Window (CW) 의 크기를 변경하고 Backoff 시간은 이 CW의 크기에 따라 확률적으로 결정된다. 따라서 CW의 크기는 무선 네트워크의 상태를 나타내는 중요한 지표가 될 수 있다. 본 논문에서는 상대적으로 넓은 공간에서 IEEE 802.11a 무선네트워크의 Access Point와 사용자들이 Poisson point process (PPP)를 기반으로 분포되어 Hidden Terminal이 존재할 수 있는 상황에서 CW의 크기 변화를 시뮬레이션을 통해 분석한다.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1594-1597
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• 2002

In this paper, we proposed the IEEE 802.11 CSMA/CA protocol with the priority scheme. The IEEE 802.11 CSMA/CA protocol is the standard in wireless LAN We applied the proposed method to the aeronautical mobile telecommunication environment. The CSMA/CA protocol has two frames : one is PCF frame for real time service like voice and image and the other DCF frame for contention services like data transmission. Now we proposed the priority scheme that has the different CW region according to the transmitted data. The simmulation results shows the proposed method's performance is improved, Because the collision probability is reduced by allowing the different CW between stations. And the time dalay results show the priority scheme is very appropriated.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.47-48
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• 2006

In this paper, we analyze the impact of superframe order on the performance of the IEEE 802.15.4 slotted CSMA/CA. A new analytic model to evaluate the saturation throughput is proposed. The new model describes slot time behaviors of the IEEE 802.15.4 slotted CSMA/CA. The proposed model is validated via the comparison with ns-2 simulation results.

• 한국정보통신학회논문지
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• 제3권1호
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• pp.75-82
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• 1999

무선 실시간 모니터링 시스템은 무선 모뎀, 중앙 모니터, 이동단말기, 데이터베이스 서버로 구성되며 환자의 이동성, 설치시간의 감소, 장기간으로 본 비용절감 등의 잇점을 제공한다. 또한 이 시스템은 환자 위치추적 서비스를 제공한다. 환자 위치 추적 서비스는 무선 모니터링 시스템의 경우 환자 이동중 위급 상황 발생시 응급 처치를 위해 반드시 제공되어야 한다. 본 논문에서는 개선된 CSMA/CA프로토콜과 환자 위치 추적 알고리즘을 제안하고 이를 이용하여 무선 실시간 모니터링 시스템을 구현하였다.