• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.10
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• pp.2457-2464
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• 2015

Distributed Networked Control Systems (NCSs) through wireless networks have a tremendous potential to improve the efficiency of various control systems. In this paper, we define the State Update Interval (SUI) as the elapsed time between successful state vector reports derived from the NCSs. A simple expression of the SUI is derived to characterize the key interactions between the control and communication layers. This performance measure is used to formulate a novel optimization problem where the objective function is the probability to meet the SUI constraint and the decision parameter is the channel access probability. We prove the existence and uniqueness of the optimal channel access probability of the optimization problem. Furthermore, the optimal channel access probability for NCSs is lower than the channel access probability to maximize the throughput. Numerical results indicate that the improvement of the success probability to meet the SUI constraint using the optimal channel access probability increases as the number of nodes increases with respect to that using the channel access probability to maximize the throughput.

• Convergence Security Journal
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• v.15 no.5
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• pp.17-22
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• 2015

As financial deregulation policies implemented by the government, electronic financial service is improved but security concerns are increasing and ultimately weaken trust in the financial service. Electronic financial service becomes more and more dependant on the IT platform and the initiatives of access device is also gradually shift to that platform. As biometric sensor is mounted on the smartphone, structural change in the access device is coming. It must be a positive signs in terms of fintech development, in the other side, it can cause many problems such as weakness of regulation and ambiguity of principals of responsibility. So in this paper, by analysing this problem-the shift of service initiative-on the access device I'll propose the best way to the the legal amendments.

• The Journal of the Acoustical Society of Korea
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• v.34 no.6
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• pp.463-469
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• 2015

In this paper, we propose an underwater propagation delay-aware medium access control protocol and evaluate the performance of the proposed protocol. In the proposed propagation delay-aware medium access control protocol, a sink node can restore the received RTS frames that are not piled up in a slot time. We analyze and compare the performance of the proposed underwater propagation delay-aware medium access control protocol with that of the conventional medium access control protocol in various environments.

• Information and Communications Magazine
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• v.15 no.2
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• pp.61-82
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• 1998

무선 ATM의 MAC 프로토콜은 독립적으로 분산되어 있는 이동 단말기들을 대상으로 ATM이 추구하는 진정한 의미의 통계적 다중화 기능을 무선 매체를 통해 확장하는 역할을 한다. 이와 같은 매체 접근 제어 프로토콜을 통해서만 멀티미디어 서비스 특성에 따라 동적으로 변하는 대역 요구 사항과 지연 시간 및 셀 손실 등의 서비스 품질을 동시에 만족시킬 수 있으며, 이동 단말기들이 채널을 공평하면서도 효율적으로 사용할 수 있는 접속 환경을 제공할 수 있다. 따라서, 이와 관련한 유럽의 ACTS 프로젝트 및 제외국에서의 기술 개발 사례와 ATM Forum WATM-WG에서의 표준화 동향을 분석하여 향후 무선 ATM 구현에 필요한 요소 기술로서의 매체 접근 제어 방식의 설계 및 구현 방안에 대해서 고찰함으로써 향후 연구 방향을 제시하고자 한다.

• The KIPS Transactions:PartC
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• v.9C no.4
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• pp.523-530
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• 2002

Earlier efforts on optical access concentrated on the design of PONs for the collection and distribution portion of the access network. PON architecture is very simple but it requires MAC protocol for control of upstream traffic. This paper proposes a MAC protocol for a broadband access network using an ATM Passive Optical Network supporting CBR/rtYBR, nrtYBR, UBR and ABR traffic. For the proposed MAC scheme, we present grant field format, minislot format, and bandwidth allocation algorithm. From the simulation result, we have confirmed that our proposed scheme can reduce the average cell delay in comparison to that of conventional MAC schemes.

• The KIPS Transactions:PartC
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• v.13C no.5 s.108
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• pp.567-574
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• 2006

VG-AnyLAN is a local area network standard developed by the IEEE 802.12 project. While preserving the frame format of IEEE 802.3, VG-AnyLAN adopts a new medium access control called Demand Priority where transmission requests of stations are arbitrated by a control hub in a round-robin manner. Unlike CSMA/CD which is the medium access control of IEEE 802.3, the Demand Priority, while providing the maximum bound on the packet delay, does not put the limit on the network segment size. In this paper, we analyze the delay and the channel utilization performances of the medium access control of IEEE 802.12 VG-AnyLAN. We develope an analytic model of the system under assumptions that each station generates traffic of the equal priority and that the packets are of fixed length. Using the analytic model, we obtain the recursive expression of the average channel utilization and the average access delay The numerical results obtained via analysis are compared to the simulation results of the system for a partial validation of our analysis.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.5A
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• pp.809-816
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• 2001

본 논문에서는 사용자 수의 증가에 민감하지 않은 안정적인 인터넷 서비스를 위한 매체접근제어 프로토콜을 제안하고자 한다. 제안하는 프로토콜에서는 짧은 시간동안 적은 양의 데이터가 발생하는 상향채널 인터넷 트래픽의 특성 및 음성과 데이터 연결이 동시에 설정되는 다중 세션 모드를 활용하여 음성 트래픽 채널을 통해 상향채널 인터넷 트래픽을 전송할 수 있는 방안을 제시한다. 수학적 분석 시뮬레이션 결과는 다중세션 하에서 제안하는 매체접근제어 프로토콜을 적용할 경우 높은 시스템 부하에서도 안정된 인터넷 서비스 제공이 가능함을 보인다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.709-716
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• 2006

본 논문에서는 무선 센서 네트워크의 다양한 응용 환경 및 상/하향 트래픽 스트림의 특성에 따라 유연하게 적용할 수 있는 새로운 매체접근제어 프로토콜을 제안한다. HiPERMAC(Hierarchically-Paired Evolutionary Radio MAC)이라고 불리는 제안 매체접근제어방식은 다양한 클러스터링 방식에 의하여 구축된 다 계층 (Hierarchical) 네트워크에서 별도의 대역 확산 전송방식이나 다수의 주파수 채널을 사용하지 않고, 단 2개의 시간 구간을 공간적으로 재활용하여 N 계층의 개별적인 통신이 가능한 구조를 제공한다. 즉, 제안방식은 단일 주파수 개념을 이용하여 계층화된 우선 센서 네트워크를 계층적 이중화(Hierarchically-Paired)하고 이때 발생하는 클러스터 간 상호 간섭의 요인들을 시간 및 공간적으로 분리하여 망 확장성과 자원 효율성을 극대화 하는 새로운 매체접근 제어 방식 이다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.5B
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• pp.365-377
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• 2006

We define the incomplete medium sharing system as a multi-channel shared medium communication system where any types of constraints are imposed to the set of channels that may be allocated to any transmitter-receiver node pair. A set of distributed MAC schemes are proposed, all of which are based on the CSMA/CA scheme employed in IEEE 802. 11 WLAN standards. Distributed MAC schemes are proposed in three different forms, which can be differentiated by the number and the location of back-off timers; that is, (1) one timer for all queues destined for different receiver nodes, (2) multiple timers at individual transmission queues, (3) multiple timers for individual channels. Through an extensive set of computer simulations, the performances of the proposed MAC schemes show that the MAC scheme with timers at individual transmission queues outperform the others in terms of throughput and delay for most cases considered. The complexity of the proposed schemes is also compared, and the first scheme obviously turned out to be the simplest, and the complexity of the second and third schemes depends on the number of receiver nodes and the number of channels, respectively.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.8A
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• pp.1195-1207
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• 1999

Wireless channel has high error rate and limited bandwidth. In order to guarantee the quality of service for multimedia through wireless channel, wireless ATM network requires the cell structure with error control schemes and an efficient medium access control protocol. In this paprt, an efficient medium access control protocol, which is considered of cell structure and the QOS, is proposed for wireless ATM networks. Many kinds of ATM cell structures are analyzed in terms of cell error rate and cell loss rate to choose the proper cell structures for this proposed MAC protocol. And a bandwidth allocation algorithm is also designed to satisfy the priority of services. The performance of proposed MAC protocol are evaluated in terms of channel utilization, call blocking and packet discard probability accotding to different kinds of cell structure through simulation.