• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.8 no.1
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• pp.102-109
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• 2009

This paper proposes the efficient method of CSMA during an idle duration in the time slot. The hybrid TDMA/CSMA protocol is the method that shares the medium efficiently. This improves the channel efficiency and throughput by using CSMA method during the idle TDMA time slot. In CSMA duration, many devices start to compete with each other. This causes a low throughput because of a long delay and a frequent collision. In order to improve this problem, the proposed method reduces the number of devices that compete in the CSMA duration. Because the number of competed device is reduced, this proposed algorithm reduces the delay and collision probability. This decrements of delay and collision probability improve the networks. The simulation results show that the proposed limitive CSMA methods outperform any methods of hybrid TDMA/CSMA protocol.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.5
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• pp.1208-1220
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• 1996

In this paper, the performance of a Carrier Sense Multiple Access/Collision avoidance (CSMA/CA) protocol using stop-and-Wait automatic Repeat reQuest, which is adapted as a draft standard in IEEE 802.11, is analyzed using a mathematical method based on a renewal theory, and simulation checks are performed, which confirm the goodness of our anlysis. In order to anlayze of CSMA/CA, we model that network is composed of finite populationand channel is slotted. And, we consider the CSMA/CA protocol as a hybrid protocol of 1-persistent CSMA and p-persistent CSMA protocol. As resuls of analysis, we have found that the throughput is degraded and packet delay is increased as the number of stations, Acknowledgement (ACK) length and Distributed coordination function Inter Frame Space (DIFS) length are increased.

• Journal of Communications and Networks
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• v.17 no.3
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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.

• Journal of IKEEE
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• v.2 no.1 s.2
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• pp.76-84
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• 1998

In this paper, CSMA/CA with bridging is analyzed which is an added function of relaying directly between access points when wireless terminals can not communicate each other, and is also compared to the CSMA/CA without bridging which is IEEE 802.11 MAC standard. Through simulations, it is shown that the two methods have the similar performance in terms of the throughput but the bridging CSMA/CA improves the delay compared to the non-bridging CSMA/CA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.1
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• pp.33-43
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• 2013

This paper proposes a distributed MAC protocol called Carrier Sensing Multiple Access with Collision Resolution (CSMA/CR) considering fully-connected single hop network environments for next-generation wireless LAN with high density of stations. The proposed CSMA/CR is compatible with the conventional MAC protocols by observing the operation of CSMA/CA and is able to detect a collision promptly without RTS/CTS exchange by applying the technique of CSMA/CD to wireless environments. Moreover, once a collision is detected, the dedicated resource is allocated to the next transmission and so the collision that may occur again is resolved. We investigate some implementation issues for the practicality of CSMA/CR and compare it with the typical distributed MAC protocols. The simulation results show that the proposed CSMA/CR has a low overhead as detecting a collision without the RTS/CTS exploitation and achieves always the best throughput regardless of the number of access stations, by using the reservation-based collision resolution technique.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.1
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• pp.63-70
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• 2009

The purpose of this paper is to propose a CSMA/CA protocol to reduce the delay time and increase the throughput of the original CSMA/CA protocol. In underwater environments, the efficiency of the protocol is reduced due to the increase of the propagation delay time, which results in increase of the collision possibility causing lowering of the transmission efficiency Considering this propagation delay, this paper propose to insert the STANDBY frame in a CTS packet in order to avoid the TimeOut status of the CSMA/CA protocol. According to the simulated test results, proposed protocol is increased about 20% throughput than original CSMA/CA protocol. And the more value of propagation per transmission delay 'a' is low, the more throughput of protocol is better.

• Journal of Communications and Networks
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• v.11 no.2
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• pp.175-186
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• 2009

A new medium access control (MAC) scheme embedding physical channels into multiband carrier sense multiple access/collision avoidance (CSMA/CA) networks is proposed to provide strict quality of service (QoS) guarantee to high priority users. In the proposed scheme, two priority classes of users, primary and secondary users, are supported. For primary users physical channels are provided to ensure strict QoS, whereas secondary users are provided with best-effort service using CSMA/CA modified for multiband operation. The performance of the proposed MAC scheme is investigated using a new multiband CSMA/CA Markov chain model capturing the primary user activity and the operation of secondary users in multiple bands. The throughput of secondary users is obtained as a function of the primary user activity and other CSMA/CA parameters. It is shown that the new MAC scheme yields larger throughput than the conventional single-band CSMA/CA when both schemes use the same bandwidth.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.9
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• pp.1-12
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• 1997

The performance of Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) protocol adopted as a draft standard of IEEE 802.11 wireless LAN, is analyzed by using mathematical method based on renewal theory. We introdude three kinds of CSMA/CA protocols basic, stop-and-wait and 4-Way handshake CSMA/CA with their mathematical analysis. First, a network of finite population is considered and then expand to infinite population. We model the CSMA/CA protocol as a hybrid protocol of 1-persistent CSMA and p-persistent CSMA protocol, and verify analaytical results by computer simulation. We have found that 4-Way Handshake CAMA/CA shows better performance than those of other two types of CSMA/CA in case of high traffic load.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.12 no.2
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• pp.148-159
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• 1987

This paper proposes CSMA/CD-TDM/SD(carrier sense multiple access/collision detection-time division multiplexing/silence detection) control scheme in bus type integrated data/voice local area networks. Simulation results show that this control scheme satisfies the lossless real-time constraints of the voice traffic and improves the data throughput-delay characteristics as compared to those of the CSMA/CD/MPD and the CSMA/CD-TDMA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.12A
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• pp.1006-1014
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• 2011

Recently, as CSMA technique has been increasingly adopted in various wireless networks, extensive researches to analyze the statistical characteristics of CSMA-based wireless networks have been done. Despite the ongoing efforts, there still remain many difficulties in the analysis because of unexpectable operational behavior of CSMA. Previous literature studying CSMA networks used the concept of the carrier sensing radius to reflect the carrier sensing function. However, since the carrier sensing radius based on the protocol model is not affected by the aggregate interference from other nodes, the derived statistical models cannot avoid approximation errors especially if the network is under high interference. In this paper, we propose an algorithm to derive the carrier sensing radius considering the physical model, where the carrier sensing radius reflecting the aggregate interference is found. For the purpose of this, we analyze the aggregate interference model and the behavior of CSMA function. Based on the analysis, we propose an iterative approximation algorithm for the physical carrier sensing radius. Extensive simulations and results show that the proposed algorithm can contribute to considerably reduce the statistical modeling error of a CSMA network under various channel conditions.