• Journal of KIISE:Computing Practices and Letters
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• v.14 no.1
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• pp.101-105
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• 2008

This paper proposes an analytical model to calculate VoIP (Voice of IP) capacity over wireless LANs with frequent bit errors. Since the traditional analytical models for VoIP capacity have not included the effect of bit errors, simulations ould only evaluate VoIP capacity over erroneous channels. For analytically accurate estimation of VoIP capacity over noisy channels, we extend the conventional model to include the effect of propagation errors, end-to-end delay, voice quality, the waiting time in AP(Access Point). The experiments show that our model predicts the VoIP capacity of a given network within the range from 3% to 9% difference comparing with the simulation results.

• Journal of the Korea Society of Computer and Information
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• v.13 no.6
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• pp.225-232
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• 2008

When a single source of multimedia contents is distributed to multiple reproduction devices, the audio and video contents require synchronous play for multi-channel stereo sound and lip-synchronization. The multimedia system in vehicle, especially, has researched to move to wireless environments from legacy wired environments. This paper proposes the advanced algorithm for providing synchronized services of real-time multimedia traffic in IEEE 802.11 WLANs [1]. For these, we implement the advanced IEEE 1588 Precision Time Protocol [2] and the environments for simulation. Also, we estimate and analysis performance of the algorithm, then we experiment and analysis after the porting of algorithm in wireless LAN devices (Linksys wrt-350n AP network device) to characterize timing synchronization accuracy.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.3
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• pp.602-608
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• 2014

Smartphones have become commonplace to use smart, BYOD (Bring Your Own Device) spread the trend of domestic WLAN use is intensifying as a result, the security threat will be greatly increased. Even though WLAN vendors such as Cisco Systems Inc,. Aruba networks released WIPS, MDM, DLP etc, however, these solutions can not be easily introduced for small business due to high cost or administrative reasons. In this paper, without the introduction of expensive H/W equipment, in WLAN environments, packet analysis, AP, Station management, security vulnerabilities can be analyzed by the proposed intrusion detection system.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.8
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• pp.900-908
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• 2012

Owing to the proliferation of smart phone users, a proactive spectrum policy is needed in order to deal with increasing data traffic. Therefore, the prediction of frequency requirements for future wireless local area network (WLAN) as well as a licensed cellular communication is necessary. In this paper, we proposed a new prediction method for WLAN spectrum requirements. This method includes both a traditional prediction method and an offloading percentage from cellular network, Also, it can consider a frequency interference between access points using a statistical approach. Based on these approaches, we can predict the spectrum requirements of future domestic WLAN services considering the frequency interference. Finally, we suggest the spectrum policy for WLAN which can prevent spectrum shortage of future WLAN services.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.11
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• pp.2411-2418
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• 2011

The most typically utilized positioning method in the existing indoor WPS that is a positioning method utilizing distributed wireless network is the finger print. Its positioning is carried out by calculating the difference between the AP information map and WiFi AP signal collected. However, there are problems like low accuracy and high cost when the existing method and the radio map formation are applied to outdoors. In this paper, the characteristics of the existing WPS are surveyed and their problems are examined. In addition, we propose a new WPS using weak signal and a method to construct radio map in order to solve the above problems. And then, the results of experimental test will be analyzed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9A
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• pp.717-727
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• 2003

The HIPERLAN/2(HIgh PERformance Local Area Network Type2) is one of the wireless LAN standards for providing raw data rates of up to 54 Mbps. The MAC protocol of HIPERLAN/2 is based on TDMA/TDD, and resources in one MAC frame can be allocated dynamically by Access Point(AP). The random channel(RCH) is defined for the purpose of giving a mobile terminal the opportunity to request transmission resources in the uplink MAC frames. It is desirable that the number of RCHs is dynamically adapted by the AP depending on the current traffic situation. Allocation of excessive RCHs may waste radio resources and insufficient RCHs compared to traffic loads may result in many collisions in access attempts. We propose an RCH allocation scheme based on split algorithm in HIPERLAN/2. The simulation and analytic results show that the proposed scheme achieves a higher channel throughput, lower access delay and delay jitter than previously proposed RCH allocation schemes.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2023.11a
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• pp.135-136
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• 2023

This study is an empirical result for building an onboard communication network using metal surface wave communication and is a consideration of its application within the ship. Over the past three years, the applicability and the performance of metal surface wave communication has been confirmed by testing on five small and medium ships. In the tests, IEEE 802.11 protocol of Wi-Fi was used, and the signals were generated in the form of surface waves. Data was sent from AP to AP in the point-to-point form, and the transmission speed was measured at the same time. If necessary, additional repeaters were used to extend the transmission distance. As derived a transmission speed of 5 to 100 Mbps in wireless communication restricted areas of the 5 ships, it is believed that it is possible to reduce the weight of ships and costs by eliminating the communication cables by using surface wave communication as the back-bone network on ships.

• Annual Conference of KIPS
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• 2024.05a
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• pp.137-140
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• 2024

가상 및 증강현실(VR/AR), 원격 제어, 산업 자동화를 위한 실시간 애플리케이션이 증가함에 따라 무선 통신 네트워크의 처리량과 지연시간 성능이 중요해졌다. 이에 따라 Wi-Fi 8 에서는 초고신뢰 (Ultra-High Reliable, UHR)을 목표로 표준화가 진행 중이며 다수의 AP가 협력하여 데이터를 전송하는 다중 AP 협력 기법이 핵심 기술로 논의되고 있다. 하지만 기존의 다중 AP 협력 환경에서 협력 전송을 위한 제어 정보로 인한 간섭 증가와 OBSS(Overlapped Basic Service Set) 간섭 문제를 고려하지 못하고 있다. 따라서 본 논문에서는 효율적인 다중 AP 협력 전송을 위한 단순화된 채널 관리 방법(Simplified Channel Management Mechanism, SCMM)을 제안한다. 실험 결과에 따르면, SCMM 이 종래모델 대비 처리량은 평균 21.23% 증가했고, 지연시간은 평균 51.02% 감소했다.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.418-420
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• 2005

IEEE 802.11 에서 현재까지 많이 연구되어진 주제는 노드들 간의 공평성(fairness)에 중점을 두거나 처리율(throughput)을 높이는데 초점을 맞추어 진 것들이었다. 전체 처리율을 높이는데 AP의 백오프 방식에 관련해서는 노드들 간에 관한 연구에 비하여 비교적 연구가 적은편이다. 현재 AP와 노드들은 충돌이 발생하면 BEB(Binary Exponential backoff) 방식으로 셋팅되어 사용하고 있기 때문에 1:N의 불공평한(unfairness) 상황이 발생한다. 하향링크(downlink)가 대부분인 환경에서 AP가 다른 노드들과 같은 채널 접근확률을 가진다는 것은 바람직하지 않다. 따라서 AP가 노드들보다 우선권(priority)을 높여서 처리율을 높이는 방안이 필요하다. 그래서 본 논문에서는 AP의 백오프 방식 및 CW(Contention Window)가 변화하는데 따라서 전체 처리율에 어떤 영향을 끼치는가와 노드 수에 따른 AP의 적절한 전략 과 백오프 CW값을 분석해 보았다.

• Journal of Advanced Navigation Technology
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• v.10 no.1
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• pp.34-40
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• 2006

Multiple wireless devices in wired and wireless heterogeneous networks communicate with counterparts via a single Access Point (AP). In this case, the AP becomes a bottleneck of the network, therefore buffer overflows occur frequently and result in TCP performance degradation. In this paper, the new algorithm that prevents buffer overflows at AP and enhances TCP fairness is proposed. Depending on the buffer usage of AP, the new algorithm adaptively controls each TCP senders' transmission rate, prevents buffer overflows and thus guarantees improved TCP fairness. It is proved that the algorithm makes better of TCP throughput and fairness by preventing buffer overflows.