• 제어로봇시스템학회:학술대회논문집
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• 1988.10a
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• pp.390-395
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• 1988

The implementation of MAP(Manufacturing Automation Protocol) NIU(network interface uint) is studied and presented in this paper. Hardwares and system softwares for network management, user interface, and medium access control are developed. Also LLC(Logical Link Control) protocol is implemented. Afterwards, The operations of NIU using self-test functions are tested. Compatibility between interfaces according to IEEE 802.4 standard is also tested.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.5
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• pp.1646-1652
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• 2010

The communication in wireless sensor network is divided into several layers, because of each of them do their role, the wireless communication is possible, the MAC (Medium Access Control) layer of the one of sensor network communications layer is used to the data errors, control flow, and manage resources. Using MAC Protocol, it ensures the communication between sensor node. In this paper, highlighted the energy efficiency of the S-MAC, T-MAC protocol it emphasized the efficiency of energy by lessening the woken time of all nods effectively, transmitting and receiving the control packet on only necessary nods through use of a method that RTS packet is added to SYNC packet and making other nods sleep. On sending SYNC+RTS packet and receiving the packet, nod noticed that it wasn't necessary to be awaked on this period, would be in Sleep mode, demonstrated mathematically that energy is more effective than existing protocol, and simulated with MATLAB.

• Journal of Communications and Networks
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• v.15 no.6
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• pp.606-613
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• 2013

This paper proposes a complete solution of a contention-based medium access control in wireless local networks to provide station level quality of service guarantees in both downstream and upstream directions. The solution, based on the mature distributed coordination function protocol, includes a new fixed contention window backoff scheme, a tuning procedure to derive the optimal parameters, a super mode to mitigate the downstream bottleneck at the access point, and a simple admission control algorithm. The proposed system guarantees that the probability of the delay bound violation is below a predefined threshold. In addition, high channel utilization can be achieved at the same time. The numerical results show that the system has advantages over the traditional binary exponential backoff scheme, including efficiency and easy configuration.

• Journal of information and communication convergence engineering
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• v.12 no.4
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• pp.199-207
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• 2014

A new cooperative MAC protocol called the busy tone cooperative medium access control (BT-COMAC) protocol is proposed to overcome the drawbacks and maximize the advantages of existing schemes. This scheme uses a new metric called decibel power to decide an appropriate helper node. Using received power strength is more efficient in selecting an appropriate helper node, especially in a densely populated network, than the effective transmission rates used in conventional schemes. All communication nodes in a communication service area are assumed to move independently. Two performance metrics are used: System throughput and channel access delay. A performance evaluation of the BT-COMAC protocol is conducted using a computer simulation over a slow fading wireless channel, and its performance results are compared with those of four existing schemes. The numerical results show that the BT-COMAC protocol improves the system throughput by approximately 15% as compared to the best existing scheme.

• Journal of Communications and Networks
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• v.13 no.5
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• pp.463-471
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• 2011

Cooperative communications using relays in wireless networks have similar effects of multiple-input and multiple-output without the need of multiple antennas at each node. To implement cooperation into a system, efficient protocols are desired. In IEEE 802.11 families such as a/b/g, mobile stations can automatically adjust transmission rates according to channel conditions. However throughput performance degradation is observed by low-rate stations in multi-rate circumstances resulting in so-called performance anomaly. In this paper, we propose active relay-based cooperative medium access control (AR-CMAC) protocol, in which active relays desiring to transmit their own data for cooperation participate in relaying, and it is designed to increase throughput as a solution to performance anomaly. We have analyzed the performance of the simplified AR-CMAC using an embedded Markov chain model to demonstrate the gain of AR-CMAC and to verify it with our simulations. Simulations in an infrastructure network with an IEEE 802.11b/g access point show noticeable improvement than the legacy schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.11
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• pp.4436-4452
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• 2015

The IEEE 802.15.6 standard is introduced to satisfy all the requirements for monitoring systems operating in, on, or around the human body. In this paper, analytical models are developed for evaluating the performance of the IEEE 802.15.6 CSMA/CA-based medium access control protocol for wireless body area networks (WBAN) under unsaturation condition. We employ a three-dimensional Markov chain to model the backoff procedure, and an M/G/1/K queuing system to describe the packet queues in the buffer. The throughput and delay performances of WBAN operating in the beacon mode are analyzed in heterogeneous network comprised of different user priorities. Simulation results are included to demonstrate the accuracy of the proposed analytical model.

• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.581-584
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• 2003

본 논문에서는 링크 상황에 따라서 변복조 방식과 코딩 방식을 달리하는 기술인 AMC(Adaptive Modulation and Coding)기능과 연동하는 2 단계 ARQ(Automatic Repeat Request)방식을 제안하여 한정된 무선채널을 여러 종류의 서비스와 여러 가입자가 동시에 공유하는 경우에 발생되는 QoS(Quality of Service) 문제를 해결하고자 한다. 제안한 2 단계 ARQ 방식은 MAC(Medium Access Control) 계층에 위치하여 상위 계층으로부터 IP(Internet Protocol) packet 를 수신한 후 2 단계의 ARQ 동작을 수행함으로써 물리 채널에서 전송 중에 발생되는 오류 확률을 감소시킨다. 따라서 TCP(Transmission Control Protocol)단에서의 재전송 감소에 의한 향상된 성능도 기대할 수가 있겠다.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06d
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• pp.187-189
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• 2012

The medium access control (MAC) protocol is designed only for single channel in the IEEE 802.11 standard. That means the throughput of the network is limited by the bandwidth of the single channel. The multiple channels can be exploited to get more concurrent transmission. In this paper, we propose a novel Multi-channel MAC that utilizes the channel more efficiently than other Multi-channel MAC protocols.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.600-609
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• 2009

The traditional carrier sense multiple access (CSMA) protocol like IEEE 802.11 Distributed Coordination Function (DCF) does not handle the constraints adequately, leading to degraded delay latency and throughput as the network scales are enlarged. We present more efficient method of a medium access for real-time wireless sensor networks. Proposed MAC protocol is like the randomized CSMA protocol, but unlike previous legacy protocols, it does not use a time-varying contention window from which a node randomly picks a transmission slot. To reduce the latency for the delivery of event reports, we carefully decide to select a fixed-size contention window with non-uniform probability distribution of transmitting in each slot. We show that the proposed method can offer up to severaansimes latency reduction compared to legacy of IEEE 802.11 as the size of the sensor network scales up to 256 nodes using widely using network simulation package,caS-2. We finally show that proposed MAC scheme comes close to meet bounds on the best latency being achieved by a decentralized CSMA-based MAC protocol for real-time wireless sensor networks which is sensitive to delay latency.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7B
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• pp.463-471
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• 2007

Because of MANET's dynamic characteristic, the hidden node problem can happen. Thus it must use with distributed channel access. In Ad hoc networks, carrier sense multiple access with collision avoidance(CSMA/CA) is one of the most widely used medium access control(MAC) schemes for asynchronous data traffics. However, CSMA/CA could not guarantee the quality of multimedia traffics. CSMA is a contention based protocol. Therefor once a node gets a channel, it can momopolze. Thus the fairness problem with channel starvation will happen. We will propose a new MAC protocol to guarantee QoS for multimedia data in ad hoc networks.