• Proceedings of the Korean Information Science Society Conference
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• 2003.10c
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• pp.133-135
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• 2003

본 논문에서는 IEEE 802.11 WLAN $^{[1]}$ 에서 QoS를 제공하기 위해 새로운 MAC­layer 구조를 제안한다. 주요 특징으로는 향후 Core Network의 모델로서 제시되고 있는 DiffServ 구조의 특징들을 WLAN에 적용하는 것을 들 수 있으며, 이를 통해 다양한 종류의 멀티미디어 트래픽에 적용될 End­to­end QoS를 보다 효율적 보장하고자 한다. DiffServ에서 제시되고 있는 Expedited. Assured forwarding과 일반적인 Best­effort traffic에 대한 service 차등화 기법을 WLAN에서 적용하기 위해 기존 MAC layer에서의 DCF, PCF 대신 EDWM(Extended DiffServ in WLAN MAC)이라는 새로운 MAC­layer 구조를 제시한다. 이를 통해 시간지연에 민감한 Expedited forwarding과 대역폭의 보장을 필요로 하는 Assured forwarding의 요구 사항(QoS)을 효율적으로 보장할 수 있다. 이에 더하여 기존의 인프라(infrastructure)인 IEEE 802.11b 환경의 DCF와 이를 통하여 service를 제공받는 일반적인 Best­effort traffic을 위한 backward compatibility 보장 방안을 제시한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.8
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• pp.841-848
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• 2013

In order for unlicensed devices to co-exist on the same frequency band, the frequency interference mitigation policy is necessary. Because the effects of frequency interference between unlicensed devices may vary depending on the analysis layer, exact interference analysis must be proceeded before making any related spectrum policy. In this paper, a frequency interference between WLAN and WPAN systems that operate at 2.4 GHz ISM band were analyzed in the physical layer and MAC layer, respectively. From the results, we confirmed that the interference analysis in MAC layer is closer to the measured results. Based on these investigations, we suggest a new co-existence criterion for unlicensed devices in MAC layer.

• Journal of IKEEE
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• v.13 no.1
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• pp.94-100
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• 2009

In recent years, the wireless mesh network (WMN) has been an emerging technology to provide Internet access to fixed and mobile wireless devices. The main goal of this paper is the design and simulation of a new MAC protocol based on the multi-path routing information for wireless mesh networks. The information about multiple paths discovered in the network layer is exploited by the MAC layer in order to forward a frame over the best hop out of multiple hop choices. The performance of our approach is compared with conventional 802.11 MAC through the simulation. The results show that our scheme exhibits a significantly better performance rather than conventional 802.11 MAC protocol in terms of packet overhead, end-to-end throughput and delay.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2811-2817
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• 2010

In this paper we propose the QAC-MAC that supports Quality of Service(QoS) and saves energy resources of the sensor node, and hence prolonging the lifetime of the sensor network with multiple sink nodes. Generally, the nodes nearest to the sink node often experience heavy congestion since all data is forwarded toward the sink through those nodes. So this critically effects on the delay-constraint data traffics. QAC-MAC uses a hybrid mechanism that adapts scheduled scheme for medium access and scheduling and unscheduled scheme based on TDMA for no data collision transmission. Generally speaking, characteristics of the real-time traffic with higher priority tends to be bursty and has same destination. QAC-MAC adapts cross-layer concept to rearrange the data transmission order in each sensor node's queue, saves energy consumption by allowing few nodes in data transmission, and prolongs the network lifetime.

• Journal of Korea Multimedia Society
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• v.15 no.12
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• pp.1464-1474
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• 2012

In this paper, we propose a QoS (Quality of Service)-aware and cooperative resource reservation scheme using cross-layer link adaptation for wireless high definition video transmission through UWB (Ultra Wide Band) network with D-MAC (Distributed Medium Access Control). A wireless high definition video transmission system usually requires stable high throughput even without line-of-sight, e.g., a destination device in another room separated by a wall. Since the WiMedia D-MAC supporting DRP (Distributed Reservation Protocol) scheme causes lots of DRP resource reservation conflicts due to failure of beacon detection in wireless channel environment, overall performances of the WiMedia D-MAC can be deteriorated. And the current WiMedia MAC standard has not considered QoS provisioning even though QoS parameters such as a range of service rates are provided to each traffic stream. Therefore, we propose Relay DRP protocol with QoS-based relay node selection criterion, which makes a relay path to avoid DRP resource reservation conflicts and guarantee QoS more stably through cross-layer link adaptation of cooperative relay transmission scheme and is compliant with the current WiMedia D-MAC protocol. Simulation results demonstrate performance improvements of the proposed method for throughput and QoS provisioning.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.34 no.8A
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• pp.640-647
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• 2009

IEEE 802.11i is an amendment to the original IEEE 802.11/b,a,g standard specifying security mechanism by stipulating RSNA for tighter security. The RSNA uses TKIP(Temporal Key Integrity Protocol) and CCMP(Counter with CBC-MAC Protocol) instead of old-fashioned WEP(Wired Equivalent Privacy) for data encryption. This paper describes a design of a communication security engine for IEEE 802.11i MAC layer. The design includes WEP and TKIP modules based on the RC4 encryption algorithm, and CCMP module based on the AES encryption algorism. The WEP module suffices for compatibility with the IEEE 802.11 b,a,g MAC layer. The CCMP module has about 816.7Mbps throughput at 134MHz, hence it satisfies maximum 600Mbps data rate described in the IEEE 802.11n specifications. We propose a pipelined AES-CCMP cipher core architecture, which has lower hardware cost than existing AES cores, because CBC mode and CTR mode operate at the same time.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.9
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• pp.1158-1165
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• 2021

This paper proposes a CNN accelerator which is optimized Pooling layer operation incorporated in Multiplication And Accumulation(MAC) to reduce the memory size. For optimizing memory and data path circuit, the quantized 8bit integer weights are used instead of 32bit floating-point weights for pre-training of MNIST data set. To reduce chip area, the proposed CNN model is reduced by a convolutional layer, a 4*4 Max Pooling, and two fully connected layers. And all the operations use specific MAC with approximation adders and multipliers. 94% of internal memory size reduction is achieved by simultaneously performing the convolution and the pooling operation in the proposed architecture. The proposed accelerator chip is designed by using TSMC65nmGP CMOS process. That has about half size of our previous paper, 0.8*0.9 = 0.72mm². The presented CNN accelerator chip achieves 94% accuracy and 77us inference time per an MNIST image.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.336-340
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• 2007

This paper proposes a multicast scheme over IEEE 802.16 networks which support multiple upper layer protocols such as ATM, IPv4 packets, IPv6 packets, IEEE 802.3 over IPv4 and so on. The multicast capabilities over IEEE 802.16 are important both control plane and data plane. The proposed multicast scheme can be divided into two types: direct mapping and indirect mapping. The direct mapping scheme is that layer 3 address is directly mapped into CID information which is used for connection identifier at IEEE 802.16 link layer. The indirect mapping scheme has two steps for mapping between layer 3 address and layer 2 CID. Firstly, a layer 3 address translates to Ethernet MAC address with group MAC address. Secondly, a group MAC address is mapped into CID. The mapping scheme depends on the upper layer protocols.

• Electronics and Telecommunications Trends
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• v.11 no.4 s.42
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• pp.89-101
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• 1996

본 논문은 IEEE 802.11 프로토콜 구성과 무선 근거리 통신망의 매체접근제어(Media Access Control: MAC), 공유자원인 무선채널을 액세스하기 위하여 사용하는 대표적인 MAC방식을 분류하여 설명하였고, MAC의 핵심이 되는 매체접근제어 프로토콜인 DFWMAC(Distributed Foundation Wireless MAC)의 핵심기능에 대하여 소개한다.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.427-428
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• 2008

본 논문에서는 IEEE 802.11 MAC Layer의 Reception, Transmission 검증을 위해 PLI (Programing Language Interface)를 이용한 방법을 제안한다. PLI를 이용한 검증은 시스템 Level의 검증으로써 설계단계에서 문제점을 확인하고 수정할 수 있다. 그러므로 불필요한 개발비의 낭비를 줄일 수 있고 개발 기간 단축의 효과를 거둘 수 있다. 검증을 위해 Mentor Graphics 사의 HDL (Hardware Description Language) 시뮬레이터인 Modelsim 6.1g Version을 사용하고 PLI를 이용하여 검증 환경을 구축한다.