• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.3A
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• pp.267-277
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• 2011

Like other wireless network protocols, IEEE 802.15.4 adopts CA (Collision Avoidance)algorithm to avoid the early collision of a new packet by randomizing its first transmission time rather than its immediate delivery. The traditional CA scheme of IEEE 802.15.4, however, selects the random access time from the predetermined range without considering the degree of current congestion. It probably causes either a long delay to settle in the suitable range for the current network load or frequent clashes especially during the long lasting heavy traffic period. This paper proposes an ACA(Adaptive Collision Avoidance) algorithm adapting the initial backoff range to the undergoing collision variations. It also introduces a mathematical model to predict the performance of ACA algorithm added to IEEE 802.15.4. With only small deviations from corresponding simulations, our analytical model shows that ACA technique can improve the throughput of IEEE 802.15.4 by up-to 41% maximally in addition to shortening the packet delays.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1B
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• pp.9-14
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• 2012

The neighbor discovery using directional antennas in mmWave band is a prerequisite for communications and this issue is crucial and urgent. In this paper, the synchronized, direct, two-way directional neighbor discovery process is analyzed mathematically for mmWave WPANs. The analysis is based on the values which are derived from the effect of using directional antennas. The neighbor discovery probability for a given amount of time is considered and several performance measures such as the optimal sojourn time are derived in closed forms. Numerical results are obtained using parameters based on the IEEE 802.15.3c. The mathematical analysis provides the theoretical basis for the directional neighbor discovery process.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.148-150
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• 2003

무선통신에서의 전송 매체인 air interface는 주위의 여러 환경적인 요인에 의해서 다양한 에러가 존재할 수 있다. 더욱이 ad hoc 환경인 802.15.3 High­rate WPAN에서는 이러한 에러에 대한 의존도가 더욱 클 수 있다. 본 논문에서는 802.15.3의 MAC enhancement를 목표로 위치에 따라서 달라지는 에러를 이용해서 할당하는 채널 시간의 크기를 동적으로 변화시켜서 전체 채널 사용 효율을 향상 시키려고 시도한다.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.2
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• pp.29-36
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• 2004

유비쿼터스 컴퓨팅 시대가 매우 빠르게 도래하면서 가정이나 회사의 정보 가전기기들이 초고속, 대용량을 전송하는 고속의 디지털 가전기기들로 바뀌어 가고 있으며 이들을 하나의 네트워크로 구성하고자 하는 요구가 증가하고 있다. IEEE 802.11과 IEEE 802.15.3a Task Group에서는 대량의 정보를 고속으로 통신하는 기술의 표준화를 위해 연구하고 있으며, 간단한 시스템을 이용하여 저속의 통신을 저렴한 가격으로 이루려는 또 하나의 주류인 ZigBee (IEEE802.15.4), Bluetooth (IEEE802.15.1) 시스템이 개발되고 있다. (중략)

• Proceedings of the IEEK Conference
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• 2004.06a
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• pp.107-110
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• 2004

IEEE 802.15.3 is wireless Medium Access Control(MAC) and Physical Layer(PHY) specification for high rate WPAN (Wireless Personal Area Network). IEEE 802.15.3 MAC Layer provides Qos with three kinds of acknowledgements; No acknowledgement, Immediate acknowledgement, and Delayed acknowledgement. This paper presents how to improve QoS with new acknowledgement method called Delayed Negative acknowledgement. This paper describes the method of using Delayed Negative acknowledgement and presents the calculation of QoS improvement by using Delayed Negative acknowledgement.

• Proceedings of the KIEE Conference
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• 2006.04a
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• pp.81-83
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• 2006

This Paper suggests efficient design method which is used by Bit_Inerleaver in the IEEE 802.15,3.a. Bit_Interleaver is consist of Symbol_Interleaver and Tone_Interleaver Each Interleaver is designed by using memory. In other to resolve burst error, Block Interleaver is using different leading and writing address for mixing the data. However This method has a different reading and writing memory address to realize Block Interleaver so this schematic is some complex. This Paper suggests efficient and simple Bit_Interleaver Method which classify the memory of Bit_Interleavr to reduce complexity of shcemeatic.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.226-228
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• 2004

IEEE 802.15.3 High-Rate WPAN(Wireless Personal Area Network)는 l0m내외의 무선 환경에서 실시간 비디오, 고품질 오디오 및 대용량 파일 전송을 가능케 하는 기술이다 하나의 네트워크를 piconet 단위로 구성하고 하나의 Piconet에는 PNC(piconet coordinator)가 TOMA(Time Division Multiple Access) 방식으로 DEV(device)들에게 채널타임을 할당한다. 본 논문에서는 IEEE 802.15.3 High-Rate WPAN 환경에서 하나의 piconet 에 존재하는 각각 통신을 하려는 DEV 들이 서로의 신호에 간섭을 받지 않을 만큼 떨어져 있다면 한 개의 채널타임을 각각의 DEV 들에게 동시에 할당하여 여러 DEV들이 동시에 통신을 하는 공간 재활용방식을 통해 네트워크의 성능을 향상하는 방법을 제안하고 MAC의 공간재활용방식을 통한 네트워크의 성능향상 방법을 연구한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.05a
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• pp.1249-1252
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• 2004

IEEE 802.15.3 고속률 WPAN(Wireless Personal Area Networks)은 네트워크 구성 시 인증을 받은 노드들에게만 통신 권한을 부여함으로써 보안성을 높였다. 그러나 IEEE 802.15.3 WPAN에서 제안한 인증 방법은 사전에 각 노드들이 중앙 집중적인 키 관리자로부터 오프라인 상으로 인증키를 분배 받는 것을 가정으로 하고 있다. 이 같은 가정은 WPAN이 무선 Ad Hoc 네트워크로서 중앙 관리 노드가 부재하고 위상 변화가 유동적인 특성을 고려하지 못한 것으로 WPAN의 확장성을 감소시킨다. 따라서 본 논문에서는 WPAN의 노드들이 온라인을 통해 협력적으로 인증키를 생성하는 분산 인증키 관리 방법을 제안한다. 이 방법은 WPAN 네트워크에 확장성을 제공할 뿐 아니라 마스터 노드에 대한 보안 의존성을 감소시켜 인증 서비스의 가용성을 증대시킨다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.3
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• pp.49-56
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• 2007

The IEEE 802.15.4 low rate wireless personal area network is a protocol suitable for wireless sensor networks. Thus there has been growing interest in the IEEE 802.15.4 protocol in the home automation networks. This paper proposes a scheduling scheme obtaining optimal parameters regarding the IEEE 802.15.4 frame and subframes in the home automation networks. Guaranteed time slots (GTS) are exploited for the delivery of real-time traffic. Given a set of the requirements for bandwidths and periods assigned to nodes in the network, the beacon interval and the active/inactive subframe duration satisfying the requirements are selected considering the low duty cycle by the proposed scheme. Based on these parameters, analytic results provide the way to efficient use of network resources including energy.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.3
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• pp.1711-1717
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• 2014

There have been many studies on IEEE 802.15.4 for home area networks(HAN) in Smart Grids. Existing unslotted or slotted IEEE 802.15.4 has almost not met strict conditions of the U.S. Department Of Energy(DOE). This study proposed a improved algorithm that reduces collisions, delay time and changes in the delay time. For this purpose, numbers were given to nodes to make the transmission in the order of the node numbers. Since the probability of the occurrence of collisions would decrease compared to random transmission if the nodes were given numbers, Backoff time was set at 0. In the proposed Numbered-Unslotted-ZeroBackoff algorithm, when the packet size was 133 octets and less than 180 packets per second occurred, it was found that packet delivery ratio was over 99.99%, and that all the maximum delay, the mean delay and the minimum delay were less than 0.02 seconds. This paper could confirm that the algorithm proposed in this study met the strict conditions of the DOE.