• IE interfaces
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• v.16 no.2
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• pp.195-200
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• 2003

In this paper, the selective use of RTS and CTS frames is considered to analyze the capacity of IEEE 802.11 WLAN (Wireless Local Area Network). The RTS and CTS frames are used to transmit the data frames longer than dot11RTSThreshold according to IEEE 802.11 specification. The analysis of the optimal RTS-CTS threshold is derived to maximize the capacity of IEEE 802.11 WLAN. And, numerical examples are also presented for IEEE 802.11 a and b WLANs.

• Journal of Korean Institute of Industrial Engineers
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• v.34 no.2
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• pp.246-254
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• 2008

In this paper, a new efficient hidden node detection method is proposed to decide whether the RTS/CTS mechanism is necessary to resolve the hidden node problem for the data transmission of each node in infrastructure mode IEEE 802.11 wireless LANs. The nodes, for which the RTS/CTS mechanism is found to be not necessary by the hidden node detection method, can transmit their data frames without performing the RTS/CTS exchange. Only the nodes, for which the RTS/CTS mechanism is found to be necessary by the hidden node detection method, perform the RTS/CTS exchange before their data frame transmissions.

• 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.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.45 no.6
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• pp.33-44
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• 2008

Multipath routing protocols with load balance, fault tolerance, aggregated bandwidth in Ad-hoc Networks provide improved throughput and reliable route as compared with singlepath routing protocols. However, multipath routing protocols have not been explored thoroughly in the domain of overhead in Ad-hoc Networks. In this paper, we analyze and compare on-demand singlepath and multipath routing with IEEE 802.11 DCF in terms of Routing overhead and MAC overhead. The results reveals that in comparison with singlepath routing protocol, multipath routing mechanism creates more overheads but provides better performance in congestion and capacity provided that the route length is within a certain upper bound which is derivable. The analytical results are further confirmed by simulation.

• Journal of Computing Science and Engineering
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• v.8 no.2
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• pp.107-118
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• 2014

One interesting problem regarding wireless local area network (WLAN) ad-hoc networks is the effective mitigation of hidden nodes. The WLAN standard IEEE 802.11 provides request to send/clear to send (RTS/CTS) as mitigation for the hidden node problem; however, this causes the exposed node problem. The first 802.11 standard provided only two transmission rates, 1 and 2 Mbps, and control frames, such as RTS/CTS assumed to be sent at 1 Mbps. The 802.11 standard has been enhanced several times since then and now it supports multi-rate transmission up to 65 Mbps in the currently popular 802.11n (20 MHz channel, single stream with long guard interval). As a result, the difference in transmission rates and coverages between the data frame and control frame can be very large. However adjusting the RTS/CTS transmission rate to optimize network throughput has not been well investigated. In this paper, we propose a method to decrease the number of exposed nodes by increasing the RTS transmission rate to decrease RTS coverage. Our proposed method, Asymmetric Range by Multi-Rate Control (ARMRC), can decrease or even completely eliminate exposed nodes and improve the entire network throughput. Experimental results by simulation show that the network throughput in the proposed method is higher by 20% to 50% under certain conditions, and the proposed method is found to be effective in equalizing dispersion of throughput among nodes.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.3
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• pp.19-25
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• 2012

Underwater sensor networks (UWSNs) employ acoustic channels for communications. One of the main characteristics of the underwater acoustic channel is long propagation delay. Previously proposed MAC (medium access control) protocols for wireless sensor networks cannot be directly used in UWSNs due to the long propagation delay. The long propagation delay and uneven nodes deployments cause spatial fairness in UWSNs. Therefore, a new MAC protocol for UWSNs needs to be developed to provide efficient communications. In this paper, we propose an efficient MAC protocol in order to alleviate the fairness problem. In the proposed scheme, when a node receives a RTS packet, it does not immediately send back but delays a CTS packet. The node collects several RTS packets from source nodes during the delay time. It chooses one of the RTS packets based on the queue status information. And then, it sends a CTS packet to the source node which sent the chosen RTS packet. The performance of the proposed scheme is investigated via simulation. Simulation results show that our scheme is effective and alleviates the fairness problem.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.8 no.6
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• pp.97-103
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• 2008

T-Lohi, a MAC protocol for underwater acoustic sensor networks, has been designed to support dense networks consisting of short-range acoustic modems. However when T-Lohi is applied to large networks in which multi-hop routing is necessary, it suffers a lot of packet collisions due to the hidden terminal problem. To combat this problem, we propose a new MAC protocol which employs RTS/CTS handshaking. To our knowledge, this protocol is the first to adopt both a tone-based approach and RTS/CTS handshaking for dense underwater acoustic sensor networks. Simulation results show that this new protocol drastically reduces packet collisions while achieving good network utilization.

• 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 Institute of Electronics Engineers of Korea TC
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• v.37 no.2
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• pp.7-16
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• 2000

In this paper, IEEE 802.11 MAC layer protocol is modeled by p-persistent CSMA method. And We introduce performance analysis model based on Basic CSMA/CA protocol, CTS/RTS protocol and hidden node effect reflected Basic CSMA/CA Protocol, Which is mathematically assayed by renewal theory. In this throughput, the result shown that Basic CSMA/CA protocol is profitable when the number of active node is smaller, or the length of packet is shorter, and CTS/RTS protocol is lucrative when the number of active node is larger, or the length of packet is longer. Also the result shown that hidden node less affected when the active node has small one, rather than when the active node has larger one.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.633-636
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• 2011

The paper deals with the performance of contention-based medium access control (MAC) protocols for underwater sensor networks. We extensively analyze the number of received-packets and the end-to-end delay of ALOHA, CSMA, CSMA-RTS-CTS and CSMA-RTS-CTS-ACK protocols using a Qualnet underwater network simulator which accommodates diverse underwater acoustic channel environments. Using simulation results, we support an engineering table to determine an adequate contention-based MAC protocol for underwater sensor networks.