• Journal of the Korea Society of Computer and Information
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• v.12 no.6
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• pp.229-234
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• 2007

In the IEEE 802.11 Wireless Local Area Networks (WLANs), network nodes experiencing collisions on the shared channel need to backoff for a random period of time. which is uniformly selected from the Contention Window (CW) This contention window is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. The BEB scheme suffers from a unfairness problem and low throughput under high traffic load. In this paper, I propose a new backoff algorithm for use with the IEEE 802.11 Distributed Coordination Function.

• The Journal of the Acoustical Society of Korea
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• v.36 no.3
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• pp.211-217
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• 2017

In this paper, we propose a bidirectional full duplex MAC (Medium Access Control) protocol for underwater acoustic networks. An underwater sensor node can set a back-off timer according to the priority of transmission. When the back-off timer expires, the underwater sensor node acquires a transmission opportunity. If a source node wants to send data to a destination node, it broadcasts RTS (Request-To-Send) including ID of the destination node to neighbor nodes. The destination node receiving RTS sends CTS (Clear-To-Send) to the source node to inform the bidirectional full duplex communication. After the source node receives CTS, the source node and the destination node can send the data to each other. In the underwater environment, the existing MAC protocol may take a lot of time for successful transmission of data due to long underwater propagation delay. On the other hand, the proposed bidirectional full duplex MAC protocol improves the throughput by shortening the time for successful transmission of data. In this paper, we analyze the throughput of the proposed bidirectional full duplex MAC protocol. In addition, we show that the proposed bidirectional full duplex MAC protocol has better performance in the presence of the long underwater propagation delay compared with existing MAC protocols for underwater environments.

• KIPS Transactions on Software and Data Engineering
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• v.3 no.11
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• pp.487-494
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• 2014

This paper focuses on an advanced congestion control scheme for M2M(Machine-to-Machine) communications in 3GPP LTE-A standard. A large number of MTC(Machine-type-Communication) devices try to access to LTE-A networks and send data to the networks all at once. In this characteristics, M2M communications will bring the serious network congestion problems into LTE-A cellular networks. To solve this critical problem, a congestion control mechanism will be required and it has been studied since Rel-10 LTE-A systems based on backoff mechanism for mobility management and session management. In this paper, we briefly introduce the main concept and operation about the congestion control scheme in 3GPP LTE-A standard. Also, simulation results for the basic congestion control and advanced congestion control scheme in MTC communication environment are provided and the improvement direction is considered in future 3GPP LTE-A standard.