• Proceedings of the IEEK Conference
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• 2003.11c
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• pp.212-215
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• 2003

본 논문에서는 IEEE 802.11e MAC (Medium Access Control) 프로토콜을 NS-2 등과 같은 유명한 시뮬레이터들보다도 진보적인 NCTUns 시뮬레이터를 이용하여 개발하고자 하면서, 각 MSDU (MAC Service Data Unit)마다 제공되어야 하는 TID (Traffic Identification) 를 결정하는 방안을 모색하고 있다. 따라서 본론에서는 IEEE 802.l1e MAC 프로토콜과 NCTUns 시뮬레이터 에 대해서 기술하며 본 논문에서 제안하는 방법에 대해서 서술한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.10
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• pp.99-109
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• 2007

IEEE 802.lie is being proposed to improve QoS by IEEE 802.11 working group. HCCA (HCF Controlled Channel Access) a centralized polling based mechanism of IEEE 802.11e, needs a scheduling algorithm that decides on how the available radio resources are allocated to the polled STAs. In IEEE 802.l1e standard Reference Scheduler is presented. Reference Scheduler Polls all STAs in a polling list by the same interval that causes ineffectively frequent polling. It increases not only the overhead but it decreases the TXOP (Transmission Opportunity) utilization. In this paper, we propose the scheduling and admission control algorithm that poll stations depending on the MSI (Maximum Service Interval)o( stations to solve these shortcomings. In our proposed algorithm a station is polled by an interval close to its MSI, so polling overhead decrease and TXOP utilization increases than Reference Scheduler. Simulation results show that our algorithm outperforms Reference Scheduler. Our algorithm maintains higher aggregate throughput and services mere stations than Reference Scheduler.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.466-468
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• 2005

본 논문의 연구에서는 IEEE 802.l1e MAC (Medium Access Control) 프로토콜을 NS-2 등과 같은 저명한 시뮬레이터들보다도 진보적인 NCTUns 시뮬레이터를 이용하여 개발하였다. 구현한 시뮬레이레션 모듈을 기반으로 다양한 측면의 실험하여 그 성능을 검정하였고, 본 논문에서는 특히 EDCA (Enhanced Distributed Channel Access)의 성능 결정에 중요한 요인이 되는 주요 파라미터에 대해서 성능을 분석하였다.

• Journal of the Institute of Electronics Engineers of Korea CI
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• v.48 no.1
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• pp.33-43
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• 2011

This paper proposes a traffic-aware TXOP adjustment algorithm for the IEEE 802.11e networks. In the proposed algorithm the access point (AP) monitors the network traffics periodically and adjusts the TXOP value of the non-QoS traffic in order to improve the network throughput while maintaining the QoS of video and voice applications. The experimental results show that the proposed algorithm outperforms the legacy IEEE 802.11e in terms of the throughput and the fairness.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2004.07a
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• pp.66-66
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• 2004

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.4
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• pp.89-99
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• 2007

In this paper, an analytic model of a sleep mode operation in the IEEE 802.16e is investigated. A mobile subscriber station(MSS) goes to sleep mode after negotiations with the base station(BS) and wakes up periodically for a short interval to check whether there is downlink traffic to it. If the arrival of traffic is notified, an MSS returns to wake mode. Otherwise, it again enters increased sleep interval which is double as the previous one. In order to consider the situation more practically, we propose the sleep mode starting threshold, during which MSS should await packets before it enters the sleep mode. By modifying the M/G/l with multiple vacations model, energy consumption ratio(ECR) and average packet response time are calculated. Our analytic model provides potential guidance in determining the optimal parameters values such as sleep mode starting threshold, minimal sleep and maximal sleep window.

• Journal of KIISE:Information Networking
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• v.31 no.2
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• pp.217-223
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• 2004

This paper proposes a new backoff scheme to improve the throughput of stations over wireless local area networks. It is designed to carry out the proposed backoff scheme using information of basic service area, such as number of stations, in terms of the throughput. Basic idea of the proposed backoff scheme is that we change the contention window size for backoff time as collisions increase. We evaluate the performance of the proposed backoff scheme using Markov model analysis and compare it with the IEEE 802.11e backoff scheme. The numerical results indicate that the Proposed backoff scheme may offer better performance than the conventional backoff scheme in terms of the throughput.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4A
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• pp.414-422
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• 2011

This paper describes a design of low-density parity-check(LDPC) decoder supporting block length 2,304-bit and code rate 1/2 of IEEE 802.16e mobile WiMAX standard. The designed LDPC decoder employs the min-sum algorithm and partially parallel layered-decoding architecture which processes a sub-matrix of $96{\times}96$ in parallel. By exploiting the properties of the min-sum algorithm, a new memory reduction technique is proposed, which reduces check node memory by 46% compared to conventional method. Functional verification results show that it has average bit-error-rate(BER) of $4.34{\times}10^{-5}$ for AWGN channel with Fb/No=2.1dB. Our LDPC decoder synthesized with a $0.18{\mu}m$ CMOS cell library has 174,181 gates and 52,992 bits memory, and the estimated throughput is about 417 Mbps at 100-MHz@l.8-V.

• Journal of Internet Computing and Services
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• v.6 no.5
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• pp.27-43
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• 2005

EAP provides authentication for each entity based on IEEE Std 802.1x Wireless lAN and RADIUS/DIAMETER protocol, and it uses certificate, dual scheme(e.g., password and token) with the authentication method. The password-based authentication scheme for authenticated key exchange is the most widely-used user authentication method due to various advantages, such as human-memorable simplicity, convenience, mobility, A specific hardware device is also unnecessary, This paper discusses user authentication via public networks and proposes the Split Password-based Authenticated Key Exchange (SPAKE), which is ideal for both authenticating users and exchanging session keys when using a subsequent secure communication over untrusted network, And then we provides EAP authentication framework EAP-SPAKE by using it.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1551-1557
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• 2006

Since subscribers, who pay the same communication fees, have a strong desire to take similar services with the other users, it is an important issue to provide fairness among those subscribers wherever they are located. Therefore, in this paper we propose a QoS packet scheduler that can provide fairness among wireless LAN terminals and evaluate its performance using computer simulation. The key idea of this scheduler is to reduce the CW value of the wireless LAN terminal that has failed in sending its packets due to channel transmission error in order to offer the wireless MM terminal a higher transmission priority which is the idea of service compensation. We evaluate its performance using NS-2 network simulator, compare its numerical results to those of IEEE 802.11e without this scheme, and conclude that this scheme can reduce throughput difference between similar wireless LAN terminals.