• Journal of information and communication convergence engineering
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• v.12 no.1
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• pp.1-7
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• 2014

A novel design of a simple circular ring with open-ended monopole antenna for wireless local area network (WLAN) applications is proposed in this article. The proposed antenna consists of an open-ended circular ring and $50-{\Omega}$ microstrip feed-line. The proposed antenna is capable of generating two separate resonant modes with good impedance-matching conditions. A prototype of the proposed antenna is designed, fabricated, and measured. Acceptable agreement between the measurement and simulation results is achieved. Experimental results show that the proposed antenna has operating bandwidths of 1.99-3.04 GHz and 5.08-6.1 GHz with a return loss of less than -10 dB, covering the required bandwidths of the 2.4/5.2/5.8-GHz WLAN standards. This is a microstrip antenna for IEEE 802.11a/b wireless local area networks applications. Meanwhile, the two-dimensional (2D) radiation patterns and three-dimensional (3D) gain performance of the antenna are also observed and discussed.

• Journal of information and communication convergence engineering
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• v.5 no.3
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• pp.205-208
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• 2007

The IEEE 802.11 is a MAC protocol which has been standardized by IEEE for Wireless Local Area Networks (WLANs). In the IEEE 802.11 WLANs, network nodes experiencing collisions on the shared channel need to backoff for a random period of time, which is uniformly selected from the Contention Window (CW). This contention window is dynamically controlled by the Binary Exponential Backoff (BEB) algorithm. However, the BEB scheme suffers from a fairness problem; some nodes can achieve significantly larger throughput than others. This paper proposes a new backoff algorithm for the IEEE 802.11 DCF scheme. This algorithm uses the hop count for considering fairness. It causes flows with high hop count to generate short backoff interval than those with low hop count, thus getting high priority. Therefore, when a collision occurs, the modified IEEE 802.11 DCF assigns higher priority to flow to be close to a destination.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.4
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• pp.309-315
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• 2018

Currently, the commercialization of the $5^{th}$ Generation (5G) service is becoming more prevalent in domestic communication network technology. This has reduced communication delay time and enabled large-capacity data transmission and video streaming services in real-time. In order to keep pace with these developments, K-water has introduced a smart process control system in water purification plants to monitor the status of the water purification process. However, since wireless networks are based on the public Long Term Evolution (LTE) network, communication delay time remains high, and high-resolution video services are limited. This is because communication networks still have a closed structure due to expense and security issues. Therefore, with 5G in its current form, it is very difficult to accommodate future services without improving the infrastructure of its communication networks. In recognition of these problems, this study implemented the authentication and management function of wireless networks on a wired network management system in the K-water Bansong water purification plant. The results confirmed that wired Local Area Network (LAN) services give a higher security performance than an expensive commercial wireless LAN system. This was achieved by using an Internet Protocol (IP) address management system of wired networks and the packet filtering function of the Layer2 (L2) switch. This study also confirmed that it is possible to create a wireless LAN service that is 3.7 times faster than the existing LTE communication network.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.3
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• pp.205-223
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• 2010

In this paper, we analyze the impact of different frame types on self-similarity and burstiness characteristics of the aggregated frame traffic from a real 802.11 wireless local area network. We find that characteristics of aggregated frame traffic are affected by both mean frame size and the proportion of specified frame types. Based on this new knowledge, an adaptative frame size optimization (AFSO) mechanism is proposed to improve the transmission efficiency by adaptively adjusting data frame size according to the proportions of different frame types. Simulation results show that our proposed mechanism can effectively regulate the burstiness of aggregated frame traffic and improve the successful delivery rate of data frames when a fixed throughput target is set for 802.11 wireless networks.

• Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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• 1997.11a
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• pp.274-288
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• 1997

본 논문에서는 무선 근거리 통신망의 프로토콜 구조를 분석한 후, 이를 바탕으로 무선 근거리 통신망에 적용 가능한 정보보호 규격을 제시하고, 관련 정보보호 메카니듬을 도출하며, 적용된 정보보호 메카니듬들을 C 언어로 시뮬레이션한다.

• Information and Communications Magazine
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• v.31 no.5
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• pp.73-79
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• 2014

IEEE 802.11 Wireless Local Area Network (WLAN)을 위한 전력 절약 방식에 관한 연구는 오랫동안 연구 되었음에도 불구하고 계속 발전하고 있다. 본 고는 최근 진행된 IEEE 802.11WLAN을 위한 전력절약방식에 관해 알아보고 향후 진행될 관련 연구 방향에 대해서 논의해 본다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.4B
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• pp.170-177
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• 2005

Due to the redundant rebroadcast packets, network-wide broadcasting is a costly operation in wireless mobile ad hoc networks. To reduce this redundancy, most of previous approaches implicitly or explicitly require periodic refreshing of neighborhood information which continuously imposes additional broadcast overheads. In this paper, we propose a practical broadcast pruning scheme based on the local prediction of a remained coverage area. As the proposed scheme uses only information available in the on-going broadcast process, it can minimize the overheads prevalent in previous approaches.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2215-2222
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• 2010

A Wireless Access for Vehicular Environment (WAVE) system based on Orthogonal Frequency Division Multiplexing (OFDM) is made for vehicle to vehicle wireless communications. The physical layer standard of the WAVE system is very similar to that of the IEEE802.11a wireless local area network (WLAN). Therefore, the performance of the WAVE system is degraded by continual channel variation in the WAVE multipath fading channels after starting initial channel estimation. In this paper, we research the performance improvement of equalization in 64 Quadrature Amplitude Modulation (QAM) transmission in WAVE environment. The proposed algorithms use the training sequence and the midamble sequence which is used for fast channel variation such as WAVE environments. Additionally, various interpolation methods are also used for the channel tracking.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.2
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• pp.397-406
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• 2009

A Wireless Access for Vehicular Environment (WAVE) system based on Orthogonal frequency Division Multiplexing (OFDM) is made for vehicle to vehicle wireless communications. The physical layer standard of the WAVE system is very similar to that of the IEEE802.1la wireless local area network (WLAN). Therefore, the performance of the WAVE system is degraded by continual timing delay in the WAVE multipath fading channels after starting initial timing synchronization. In this paper, the tracking algorithm that synchronizes symbol timing is proposed to continually compensate additional timing delay. Computer simulation of the proposed algorithm is performed in the worst communication environments that apply to maximum timing delay. Computer simulation shows that the proposed algorithm can improve the system performance in various channel conditions.

• Information and Communications Magazine
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• v.33 no.10
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• pp.24-30
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• 2016

본고에서는 IEEE 802.19 무선 상호공존(Wireless Coexistence) 워킹그룹(Working Group)의 구성 및 역할, TV 우휴대역 주파수 공유 시스템간 상호공존 표준기술 및 현재 논의가 진행중인 일반허가접속(General Authorized Access) 주파수 공유시스템간 상호공존 표준기술과 자동차 환경에서의 주파수 공유시스템간 상호공존 표준기술을 소개하고, 비면허대역 LTE(Long Term Evolution)와 무선랜(Wireless Local Area Network, WLAN) 시스템과의 주파수 공유 등의 무선상호공존 이슈들과 관련 표준화 동향에 대해 알아본다.