• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.3
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• pp.602-612
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• 2015

Current IEEE 802.11p which is suggested for vehicle to vehicle communication supports one hop communication. Thus, it has a limitation to carry out efficient data dissemination. In this thesis, we suggest LTE-D2D based vehicle network to provide efficient data dissemination in the vehicle environment. In this network architecture, we use name based message with IP packet options and we put the intermediate vehicle node called 'super vehicle node' and each normal vehicle node in the cell requests data to the super vehicle node. The super vehicle node responses data to the normal vehicle node. Performance analysis is based mathematical modeling. We compare LTE cellular network to LTE-D2D based vehicle network about throughput according to packet delivery time.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.478-480
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• 2003

IEEE 802.11 무선 MAC 표준은 물리 계층에서 Multirate를 제공하며. 이를 이용하기 위한 다양한 Rate adaptation 알고리즘들이 제안되었다. 일반적으로 애드 혹 무선 망은 802.11의 MAC을 기반으로 하므로 Multirate를 고려할 필요가 있다. Multirate을 지원하는 상황에서 높은 Data Rate로 통신을 할 경우, 그에 따른 높은 SNR (Signal to Noise Ratio) Threshold가 요구되므로. 기존의 RTS/CTS로는 해결할 수 없는 심각한 Hidden Terminal 문제가 발생할 수 있다. 이 논문에서는 Multirate를 지원하는 애드 혹 무선 망에서의 Hidden Terminal 문제를 분석하고 분석의 수치결과를 제시한다. 또한. Hidden Terminal 문제를 해결하기 위한 새로운 방안을 제안한다.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.113-114
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• 2007

무선 Ad Hoc 네트워크 환경에서 기존 IEEE 802.11 MAC 프로토콜에서 Omni-Directional 안테나를 이용하여 방식으로부터 자원의 활용을 늘이기 위해서 Directional 안테나를 이용한다. Directional 안테나의 사용으로 기존 802.11 MAC 프로토콜에 비해 Spatial reuse가 증가하고, 안테나의 높은 이득과 간섭의 감소, 그리고 전송범위의 증가의 장점을 갖는다. 그러나, Directional 안테나를 이용함으로서 New Hidden Problem, Deafness, 그리고 Capture 등과 같은 문제점이 발생하였다. 본 논문에서는 이러한 문제점들을 파악하고, 이를 해결하는 방안들을 분석하고 각 해결방안들에 대한 성능을 비교평가한다.

• Proceedings of the Korean Society of Computer Information Conference
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• 2009.01a
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• pp.283-288
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• 2009

고정된 망을 가지지 않고, 이동 호스트로만 이루어져 통신되는 망인 Ad-hoc 네트워크에서 고속으로 이동 중인 차량들 간의 긴급한 정보를 주고받아 고속도로에서의 다중 충돌사고를 미연에 방지할 수 있는 차량 통신 프로토콜을 제안한다. 본 논문에서는 도로위의 차량들은 서로 연계성이 없기 때문에 위치추적시스템인 GPS에서 수신한 거리 값을 연계하여 클러스터를 구성한다. 클러스터를 IEEE 802.11 MAC 계층에서 구성하기 때문에 경로 설정으로 인한 과부하문제를 해소 하였다. 논문에서 제안한 액티브 네트워크 기반의 멀티 홉 라우팅 프로토콜은, Active 네트워크를 이용하여 안정된 통신이 이루어 질수 있도록 한다.

• Journal of Information Processing Systems
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• v.4 no.2
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• pp.41-52
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• 2008

In this paper, we discuss a novel reservation-based, asynchronous MAC protocol called 'Multi-rate Multi-hop MAC Protocol' (MMMP) for multi-hop ad hoc networks that provides QoS guarantees for multimedia traffic. MMMP achieves this by providing service differentiation for multirate real-time traffic (both constant and variable bit rate traffic) and guaranteeing a bounded end-to-end delay for the same while still catering to the throughput requirements of non real time traffic. In addition, it administers bandwidth preservation via a feature called 'Smart Drop' and implements efficient bandwidth usage through a mechanism called 'Release Bandwidth'. Simulation results on the QualNet simulator indicate that MMMP outperforms IEEE 802.11 on all performance metrics and can efficiently handle a large range of traffic intensity. It also outperforms other similar state-of-the-art MAC protocols.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.507-510
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• 2011

데이터에 차별화된 우선순위를 부여하는 IEEE 802.11e EDCA는 데이터 프레임 전송 이전 스테이션 간에 발생할 수 있는 충돌을 방지할 수 없고 네트워크 환경이 혼잡할 경우에는 오히려 충돌 발생 확률을 높이는 한계가 있었다. 이 문제를 해결하기 위하여 본 논문에서는 무선 다중 애드 혹 네트워크 환경에서 채널 확보를 위한 RTS/CTS 프레임 전송 시 우선순위를 부여하여 채널을 점유할 단말을 결정하고, 또한 채널형성 후 한 노드 내에서 여러 데이터 전송 시 충돌확률을 줄이는 방법을 제안하였다.

• Journal of the Korea Society for Simulation
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• v.19 no.4
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• pp.11-19
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• 2010

ZigBee is a standard for wireless personal area networks(WPANs) based on the IEEE 802.15.4 standard. It has been developed for low cost and low power consumption. There are two alternative routing schemes that have been proposed for the ZigBee standard: Ad-hoc On-Demand Distance Vector(AODV) and tree routing. The tree routing forwards packets from sensors to a sink node based on the parent-child relationships established by the IEEE 802.15.4 MAC topology formation procedure. In order to join the network, a sensor node chooses an existing node with the strongest RSSI(Received signal strength indicator) signal as a parent node. Therefore, some nodes carry a large amount of traffic load and exhaust their energy rapidly. To overcome this problem, we introduce a new metric based on link quality and traffic load for load balancing. Instead of the strength of RSSI, the proposed scheme uses the new metric to choose a parent node during the topology formation procedure. Extensive simulation results using TOSSIM(TinyOS mote SIMulator) show that the CFR scheme outperforms well in comparison to the conventional tree routing scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.7
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• pp.1465-1470
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• 2011

In this paper, we propose a new MAC protocol, namely DM-MMAC (Doze Mode Multi-Channel MAC) for ad hoe wireless networks which can utilize multiple channels effectively, thereby enhancing the network throughput considerably. Basically, the IEEE 802.11 specification allows for the use of multiple channels available at the physical layer, but its MAC protocol is designed only for a single channel with the fatal drawback, so called multi-channel hidden terminal problem in multi-channel environments. In this vein, several multi-channel MAC protocols have been proposed, but most of them demonstrate the performance problem that its throughput drastically decreases as the number of mobile hosts residing in a given network increases with small number of available channels. In this work, we tried to improve the performance of multi-channel MAC protocols in terms of network throughput as well as power saving effects by simplifying the channel assignment and channel capturing procedures and reducing the possibility of collisions between mobile hosts.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.7
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• pp.29-35
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• 2017

This paper presents a high-throughput area-efficient mixed-radix fast Fourier transform (FFT) processor using the efficient scheduling schemes. The proposed FFT processor can support 64, 128, 256, and 512-point FFTs for orthogonal frequency division multiplexing (OFDM) systems, and can achieve a high throughput using mixed-radix algorithm and eight-parallel multipath delay commutator (MDC) architecture. This paper proposes new scheduling schemes to reduce the size of read-only memories (ROMs) and complex constant multipliers without increasing delay elements and computation cycles; thus, reducing the hardware complexity further. The proposed mixed-radix MDC FFT processor is designed and implemented using the Samsung 65nm complementary metal-oxide semiconductor (CMOS) technology. The experimental result shows that the area of the proposed FFT processor is 0.36 mm2. Furthermore, the proposed processor can achieve high throughput rates of up to 2.64 GSample/s at 330 MHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.9
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• pp.1819-1828
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• 2009

Until now, much research on cooperative communications to increase system throughput at Ad Hoc networks has been provided. In this paper, in order to enhance system throughput much more at Ad Hoc networks, a network coding-enabled new MAC protocol, called NC-MAC protocol, is proposed and its performance is evaluated with a mathematical approach. Numerical results show that this scheme provides conspicuously enhanced system throughput compared to DCF scheme, and more increased system throughput by 48% than rDCF and CO-MAC schemes.