• Journal of Advanced Navigation Technology
• /
• v.6 no.1
• /
• pp.44-51
• /
• 2002

This paper describes the performance evaluation and analysis of an Orthogonal Frequency-Division Multiplexing (OFDM) system having the least Inter Symbol Interference (ISI) in a multi-path fading channel environment. Wireless Local Area Network (W-LAN) in accordance with IEEE 802.11a and IEEE 802.11b provides high-speed transmission to universities, businesses and other various places. In addition, service providers can offer a public W-LAN service on restricted areas such as a subway. The proliferation of W-LAN has led to greater W-LAN service demands, but problems are also on the rise in offering a good W-LAN service. In particular, urban areas with high radio wave interference and many buildings are vulnerable to deteriorated QoS including disconnected data and errors. For example, when high-speed data is transmitted in such areas, the relatively high frequency generates ISI between Access Points (AP) and Mobile Terminals (such as a notebook computer), leading to a frequency selective fading channel environment. Consequently, it is difficult to expect a goodW-LAN service. The simulation proves that the OFDM system enables W-LAN to implement QoS in high-speed data transmission in a multi-path fading channel environment. The enhanced OFDM performance with 52 sub-carriers is verified via data modulation methods such as BPSK, QPSK and 16QAM based on IEEE 802.11a and punched convolutional codes with code rate of 1/2 and 3/4 and constraint length of 7. Especially, the simulation finds that the OFDM system has better performance and there is no data disconnection even in a mobile environment by applying a single tap equalizer and a decision feedback equalizer to a mobile channel environment with heavy fading influence. Given the above result, the OFDM system is an ideal solution to guarantee QoS of the W-LAN service in a high-speed mobile environment.

• Journal of the Korea Society of Computer and Information
• /
• v.15 no.7
• /
• pp.33-40
• /
• 2010

The hand over between different radio access networks, especially where their coverage overlaps, suffers various complications since the different access networks provide different service characteristics. In this paper, it is about the system which can control the wireless LAN network management system and the wireless LAN access point of variety vendor which is in different areas. Successful development of mobile sink wireless LAN network management system which supports multi-vendor devices and have center-local interoperability structure. In proposed system, speed of the mobile station give about 10% improvement when the map domain size is 5 than the existing system. Through a data plane and management system of message way, it give a stability system and consistency network.

• Journal of Navigation and Port Research
• /
• v.40 no.1
• /
• pp.43-50
• /
• 2016

Amid of the logistics hub center competition is going to intensifying between the world major port, it is essential to pre-occupied the base in the logistics hub world take advantage of advanced technology of logistics equipment than other ports. In existing container terminal, when container moves the terminal use the omnidirectional and directional antenna in order to exchange data information on the basis of 802.11 wireless network system. Case of loading height of exceeding, the blind sport will occur and a limited frequency channel can't help using in the area. A limited frequency channel usage and nested areas happen to use the closed terminal, it has a great influence to operate the terminal working. In this paper, LTE network is configured provided by the specified company ('L' Corp,.Ltd) and terminal data extracted through LBO (Local Breakout) in the cell site which is configured directly with container terminal operation server. Using this method, container terminal yard equipment operate without overlapping arises with uninterrupted data presented for ways to efficiently. I would suggest both the existing wireless AP LAN configuration of container terminal and new LTE system and applied to the real yard operating devices situations. Through these methods presented comparative the existing network traffic with new constructed LTE configuration. I admired to suggest that wireless network LTE introduction is fundamental factors to get rid of the blind spot, the problem of limited frequency channel and overlapping arises. These essential points can be a continual improving terminal services and more efficient terminal operational management.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.17 no.4
• /
• pp.159-167
• /
• 2018

In this paper, we propose an algorithm to optimize energy efficiency in a multi-user decoupled RF energy harvesting network and experiment on the trend of energy efficiency change assuming users' various geographical distribution scenarios. In the RF energy harvesting network where both wireless data transmission and RF energy harvesting are simultaneously performed, the energy efficiency is a key indicator of network performance, and it is necessary to investigate how various factors can affect the energy efficiency. In order to increase energy efficiency effectively, we can confirm that users' distributions are important factors in the RF energy harvesting network from the simulation results.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.44 no.10
• /
• pp.191-200
• /
• 2007

As the IEEE 802.11 WLAN has widely installed as a high-speed wireless network information infrastructure, there has been growing interest in both security and mobility of mobile terminals. However, for the case of mobile terminal employing IEEE 802.11i security standard, it is known that the user authentication procedure of IEEE 802.1x for stronger security enforcement may, due to its large delay, not be suitable for real-time multimedia communication. In this paper, we have proposed fast authentication method to resolve the above authentication delay problem, and verifies its performance via simulation analysis. Mobile terminals can get AP information reliably, and selectively execute authentication in advance during handover, which results in fast user authentication. In addition, by effectively managing the authentication information in mobile terminal, which are distributed in advance for pre-authentication, the problem of long-time revelation of authentication information has been solved.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.36 no.12B
• /
• pp.1474-1480
• /
• 2011

Recently the mobile IPTV service has been spread through the wireless LAN(WLAN). In order to provide the commercial mobile IPTV service through the WLAN, re-authentication for the mobile IPTV terminal is required whenever the mobile terminal roams between APs(Access Points). The most popular one of the authentication protocol standards for the wired and/or wireless LAN is IEEE 802.1X. However IEEE 802.1X takes much time to authenticate the terminal and is not adequate for the seamless mobile IPTV service. We introduce the session key and separate the user authentication and the hardware authentication. And we strengthen the device authentication by the initial registration. By these, the proposed authentication protocol reduces the authentication time and can protect the authentication key securely.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.4C
• /
• pp.581-593
• /
• 2004

The interest in wireless LAN security is on the increase owing to a role of high-speed wireless Internet infrastructure of wireless LAN. Wi-Fi has released WPA standard in order to overcome drawbacks of WEP algorithm that is security element of current IEEE 802.11-based wireless LAN system. Pairwise key management and group key management in a mixed-mode which supports both terminals running WPA and terminals running original WEP security are very complicate. In this paper, we analyze flaws in WPA authenticator key management state machine for key distribution and propose the countermeasures to overcome the analyzed problems. Additionally, WPA authenticator key management state machine to which the solutions are applied is described. The reconstructed WPA authenticator key management state machine helps the AP perform efficiently group key exchange and group key update in the mixed-mode.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.1106-1111
• /
• 2010

Conventional traffic network in the urban city has been constructed and operated under systems to collect and transmit based on the roadside AP(Acess Point). But This paper has investigated the new traffic network based on smart station which combined the power network. Futhermore, the smart station can collect and transmit the variable informations and functions that supply the vehicle moving lines, informative collector service and center interoperation etc.

• Proceedings of the Korean Information Science Society Conference
• /
• 2002.10e
• /
• pp.46-48
• /
• 2002

본 논문에서는 임베디드 시스템과 웹서버 그리고 모바일로 구성되어지는 대형 중고자동차 관리 시스템을 설계 및 구현하는 방법을 소개하고, 임베디드 시스템 내부에서는 RFID와 서버로 연결되는 네트워크의 설계를 소개하며, 모바일 장치에서의 관리와 현장의 임베디드 시스템과의 동기화 설계에 대해 논의한다. 하드웨어는 MPC860CPU 50MHz를 갖춘 XN860Core보드 및 Access Point는 ORINOCO AP-500을 사용하였으며, 임베디드 시스템의운영체제는 HardHat Linux2.0JE를 사용하였다 중고자동차 관리시스템은 관리에서 영업까지필요한 기능을 구현할 수 있도록 설계하였으며, 향후 다른 분야로 응용할 수 있도록 설계하였다.

• Proceedings of the KIEE Conference
• /
• 2008.04a
• /
• pp.253-254
• /
• 2008

본 논문은 네트워크를 통해서 시스템을 원격제어하기 위한 연구이다. 우선 이 원격제어 시스템은 AP와 무선랜을 이용하여 독립 무선 네트워크를 구축하였고 이동로봇의 주변 환경을 레이저 센서와 스테레오 카메라를 이용하여 정보를 전송한다. 스테레오 카메라를 통해 전송된 영상 정보는 HMD(Head Mounted Display)를 통하여 볼 수 있다. HMD의 회전 각도는 펜틸트에 전송되어 HMD가 회전한 만큼 펜틸트도 회전하여 이동로봇의 주변환경 영상정보를 얻을 수 있는 방법을 제안하였다.