• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3B
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• pp.100-111
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• 2008

In this paper, to support a QoS level appropriate for the user in Wireless Home Network based Wireless LAN, we propose a QoS support architecture which includes Wired Network and Wireless Network. Actually, an important problem to support QoS in Wireless Home Network is approached not only on a MAC level in Wireless LAN but on a integrated method to combine Network layer with Datalink layer. Applying the integrated QoS support method. It is possible to provide QoS support architecture using a Wireless LAN terminal with a minimum changing, the proposed scheme has advantage of QoS support method, which is more superior than a existing scheme to support QoS in MAC level of Wireless LAN. Simulation results that overall performance of the proposed scheme can be improved.

• Journal of KIISE:Information Networking
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• v.37 no.5
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• pp.386-395
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• 2010

Widespread deployment of infrastructure WLANs has made Wi-Fi an integral part of today's Internet access technology. Despite its crucial role in affecting end-to-end performance, past research has focused on MAC protocol enhancement, analysis, and simulation-based performance evaluation without sufficiently considering a misbehavior stemming from capture effect. It is well known that the capture effect occurs frequently in wireless environment and incurs throughput unfairness between nodes. In this paper, we propose a novel Fair MAC algorithm which achieves fairness even under physically unfair environment. While satisfying the fairness, the proposed algorithm maximizes the system throughput. Extensive simulation results show that the proposed Fair MAC algorithm substantially improves fairness without throughput reduction.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.6A
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• pp.640-647
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• 2006

This paper describes a design of AES-based CCMP(Counter mode with CBC-MAC Protocol) core for IEEE 802.11i wireless LAN security. To maximize the performance of CCMP core, two AES cores are used, one is the counter mode for data confidentiality and the other is the CBC node for authentication and data integrity. The S-box that requires the largest hardware in ARS core is implemented using composite field arithmetic, and the gate count is reduced by about 27% compared with conventional LUT(Lookup Table)-based design. The CCMP core was verified using Excalibur SoC kit, and a MPW chip is fabricated using a 0.35-um CMOS standard cell technology. The test results show that all the function of the fabricated chip works correctly. The CCMP processor has 17,000 gates, and the estimated throughput is about 353-Mbps at 116-MHz@3.3V, satisfying 54-Mbps data rate of the IEEE 802.11a and 802.11g specifications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.5
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• pp.31-40
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• 2010

This paper describes a LDPC decoder for IEEE 802.11n wireless LAN standard. The designed processor supports parity check matrix for block length of 1,944 and code rate of 1/2 in IEEE 802.11n standard. To reduce hardware complexity, the min-sum algorithm and layered decoding architecture are adopted. A novel memory reduction technique suitable for min-sum algorithm was devised, and our design reduces memory size to 25% of conventional method. The LDPC decoder processor synthesized with a $0.35-{\mu}m$ CMOS cell library has 200,400 gates and memory of 19,400 bits, and the estimated throughput is about 135 Mbps at 80 MHz@2.5v. The designed processor is verified by FPGA implementation and BER evaluation to validate the usefulness as a LDPC decoder.

• The Journal of the Korea institute of electronic communication sciences
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• v.8 no.5
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• pp.733-738
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• 2013

Orthogonal Frequency Division Multiplexing (OFDM) based IEEE 802.11 a/g systems which are widely used in wireless LAN carry out channel estimation in one time per packet since the systems use only preamble. Whereas, midamble based channel estimation supports continuous channel estimation by tracking the channel state information periodically. Using IEEE 802.11p Wireless Access in Vehicular Environments (WAVE) system, we analyze the performance of the proposed system via practical measurements. Based on these results, practical issues on midamble based channel estimation are investigated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.6
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• pp.1175-1180
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• 2009

Frame Aggregation is a promissing technology for improving MAC throughput in IEEE 802.11n. In IEEE 802.11n, two frame aggregation schemes, Aggregate MSDU (A-MSDU) and Aggregation MPDU (A-MPDU), are defined. In this paper, we analyze the performance the two-level frame aggregation scheme where A-MSDU and A-MPDU are combined. We develop the analytical model for the two-level frame aggregation scheme and present numerical results on the effect of bit error rate, aggregation size, and the number of nodes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.473-476
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• 2009

Frame Aggregation is a promissing technology for improving MAC throughput in IEEE 802.11n. In IEEE 802.11n, two frame aggregation schemes, Aggregate MSDU (A-MSDU) and Aggregate MPDU (A-MPDU), are defined. In this paper, we analyze the performance the two-level frame aggregation scheme where A-MSDU and A-MPDU are combined. We develop the analytical model for the two-level frame aggregation scheme and present numerical results on the effect of bit error rate, aggregation size, and the number of nodes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.2A
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• pp.168-175
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• 2006

To cope with channel variation, wireless networks such as IEEE 802.11 WLAN provide multiple transmission rates by employing different channel modulation and coding schemes. However, the coexistence of different transmission rates degrades the total system performance of the network. In order to eliminate this performance abnormality and improve protocol capacity, we propose a new Packet transmission algorithm, the RAT(Rate-Adapted Transmission) scheme. The RAT scheme distributes the wireless channel fairly based on the channel occupancy time. Moreover, it efficiently transmits packets even in a single station using rate-based queue management. Therefore, the RAT scheme obtains not only the inter-rate contention gain among stations but also the intra-rate contention gain among connections in a single station.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 2003.07a
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• pp.249-253
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• 2003

기존의 무선 랜의 보안상의 문제점들을 해결하기 위하여 사용자와 인증자사이의 상호인증과 키를 교환하는 메커니즘이 요구된다. 이것을 보안하기 위해 IEEE 802.11i에서 키 체계와 4-Way Handshake를 제안하였다. 본 논문에서 언급되는 키 생성 및 교환 메커니즘은 사용자와 서버간의 인증된 마스터키를 통한 사용자와 인증자의 상호인증과, 키 생성과 키 교환하는 방법에 초점을 맞추고 있다. 이러한 키를 생성하기 위한 Pairwise 키 체계와 키 교환을 위한 4-Way Handshake, 4-Way Handshake에서 사용되는 EAPOL-Key message에 대하여 분석하였다.

• Journal of Korea Multimedia Society
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• v.12 no.11
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• pp.1521-1529
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• 2009

There is a serious unfairness problem between upstream and downstream flows of AP in IEEE 802.11 Wireless LAN. This problem is because Wireless LAN's DCF MAC protocol provides AP with equal channel access priority to mobile noded. Also, it makes this problem worse that the TCP's Data segment loss is more effective on throughput than the TCP's ACK segment. In this paper, we first make several simulations to analysis the unfairness in the various point of view and to find reasons of the unfairness. Also, this paper presents AP's scheduling scheme to alleviate the unfairness problem and evaluate the scheme through ns2 simulator.