• Journal of Digital Contents Society
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• v.19 no.8
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• pp.1545-1554
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• 2018

In order to support the mobility of the wireless devices, at least two APs (Access Points) must be arranged in a single AP area to maintain communication area. In the WLAN (Wireless LAN) environment, seamless handover is one of the most important issues in terms of effective utilization of wireless networks and maximization of services for users. On the other hand, SDN (Software-Defined Networking), which is emerging rapidly in recent years, is revolutionizing network management in terms of flexibility, fine control, and convenience. SDN originally reduces latency time or increases network robustness by real-time flow table control reducing or bypassing paths between switches in LAN-based data centers. In this study, we apply OpenFlow, a SDN platform focused on wired LAN, to a dense WLAN environment using legacy APs to implement and evaluate seamless handover for streaming services of digital contents.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.353-362
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• 2008

Operation data and fault data are recorded at the TCMS(Train Control and Monitoring System) of train are very important record for repairs and inspection of train. there are two ways to transfer the data today. one is using memory card and the other is using wireless communications. This paper is proposed about TCMS wireless depot analytical equipment that transfers data recorded in train to depot equipment via wireless method. The TCMS wireless depot equipment configuration is an AP(Access Point) and a central server PC at depot equipment. This method has the advantage of decrease of personnel expenses, collection time and convenience of staffs. This paper is verified about the utility of use, efficient establishment position of an AP at depot, the safety of data receiving, the exactitude of data and the shortening of transmission time. and this equipment is now operating at shin-jeong depot of SeoulMetro.

• Journal of the Korea Society of Computer and Information
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• v.21 no.1
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• pp.65-72
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• 2016

Network virtualization is an emerging technology for solving the rigidity of the physical network infrastructure. The innovative technique virtualizes all resources in the network, including the network links and nodes, and provides a number of virtual networks on a single network infrastructure. In order to realize a virtual network, a thorough and complete monitoring of all resources in the network should be performed firstly. OpenFlow is an open source stack for network virtualization. However, it is impossible to apply OpenFlow to AP-based legacy wireless LAN environment because OpenFlow targets ethernet-based LAN environment. In this paper, we implement an adaptor-styled virtual switch for AP-based wireless LAN through customizing the Open vSwitch which is a virtual switch of OpenFlow. The evaluation test results show that the implemented OpenFlow stack operates successfully. The implemented OpenFlow stack can now be plugged immediately in existing AP-based wireless LAN environment and plays network resource monitoring. In the future, we can develop wireless LAN virtualization applications on the wireless OpenFlow stack.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.383-386
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• 2014

Due to the development of communication technology, a conventional major business through PC, laptop or Tablet PC can be performed via a smartphone and it is increasing the user's convenience. At this point, the user prefers to connect to the Internet using the wireless network because it occurs an additional charge according to the amount of data to be transmitted when using a data communication through 3G or 4G. However, when using a wireless network, there is a possibility of several attacks such as easily steal or modulate the information from the outside or to gain access to personal information stored in the user's smartphone with man-in-the-middle attacks by using the fake AP. IIn this paper, we describe how you can detect the AP when you use LAN of the smartphone, were analyzed for this vulnerability, has not been approved. Furthermore, Also, we discuss ways which can enhance the security when user the access to the internet services (i.e., internet, public/private cloud service, etc.) via wireless network in smartphone.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2004.05b
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• pp.41-44
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• 2004

A RFID(Radio Frequency IDentification) system Is a kind of Radio Frequency Communication System and a branch of Automatic Data Collection System. The RFID System is composed of RF Tag(or Transponder) and RFID Reader(controller). This paper deal with Wireless communications that acquired RF Tag ID by RFID reader, and then target system will transmit Tag ID to RFID Server through the internet using Wireless LAN. The RFID system of Todays are commonly used by a wired RFID system. In this system uses commonly used Wireless LAN, and then we can connect the internet if we have a AP(Wireless Lan Access Point). Internet connection can make a transmission of RF Tag ID, and can make a reception of returning data that are images or information.

• ETRI Journal
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• v.39 no.6
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• pp.794-802
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• 2017

In this paper, a wireless powered communication network (WPCN) consisting of a hybrid access point (H-AP) and multiple user equipment (UE), all of which operate in full-duplex (FD), is described. We first propose a transceiver structure that enables FD operation of each UE to simultaneously receive energy in the downlink (DL) and transmit information in the uplink (UL). We then provide an energy usage model in the proposed UE transceiver that accounts for the energy leakage from the transmit chain to the receive chain. It is shown that the throughput of an FD WPCN using the proposed FD UE (FD-WPCN-FD) can be maximized by optimal allocation of the UL transmission time to the UE by solving a convex optimization problem. Simulation results reveal that the use of the proposed FD UE efficiently improves the throughput of a WPCN with a practical self-interference cancellation capability at the H-AP. Compared to the WPCN with FD H-AP and half-duplex (HD) UE, FD-WPCN-FD achieved an 18% throughput gain. In addition, the throughput of FD-WPCN-FD was shown to be 25% greater than that of WPCN in which an H-AP and UE operated in HD.

• Journal of Internet Computing and Services
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• v.10 no.1
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• pp.33-41
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• 2009

Signals transmitted from access point (AP) or stations in different wireless LANs (WLAN) interfere each other when the WLANs are closely installed. When they are configured to use the same channel, signals from an WLAN get collided with signals from other WLANs so that the delay increases to user stations and the throughput decreases. In this paper, we propose a method in which an AP in a basic service set (BSS) detects other BSSs using the same channel and switches to a different channel not being occupied by any other BSS. We can avoid using the same channel with other BSS in spacially overlapped BSS environment. The proposed scheme is simulated and its characteristics are described with the analysis of the result. The results measured in terms of throughput show that the problems in overlapped wireless LANs can be resolved with the proposed method.

• Information and Communications Magazine
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• v.22 no.8
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• pp.114-128
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• 2005

본 연구에서는 최근 무선 네트워크 환경이 급속도로 확산되면서 발생하는 무선 네트워크 현황 및 보안 취약점을 분석하고, 센서 AP(Access Point) 기반의 무선 트래픽 필터링 및 침입탐지/차단 기술 동향을 분석하였다. 유선 네트워크를 대상으로 한 IDS/IPS 시스템에 추가적으로 무선 트래픽에 대한 모니터링 체계를 제공하기 위하여 최근에는 통합형 유무선 네트워크 침입탐지/차단 시스템을 구성하고 있으며, 이를 위해서 필수적인 센서 AP 구성 방안 및 시스템 설계 방안 등에 대한 고찰을 통해 무선 네트워크 환경에서의 침해대응 기술을 고찰해 보고자 한다.

• Proceedings of the KAIS Fall Conference
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• 2008.05a
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• pp.108-110
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• 2008

최근 무선 통신 기술의 발달은 장비를 간편화 하고 편리화 시키게 되었다. 또한 다양한 서비스를 창출 할 수 있는 기반이 마련하였다. 하지만 무선 랜의 다양한 서비스와 접속성의 확대는 보안의 취약점을 야기 시켰다. 본 논문에서는 IEEE802.11 무선 랜 서비스를 통하여 PDA 상에서 AP의 정보를 받아 무선 랜 보안 서비스의 특성과 취약성을 살펴보고 PDA 기반 위치 추적 시스템을 구현을 하였다.

• Proceedings of the Korea Multimedia Society Conference
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• 2004.05a
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• pp.17-20
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• 2004

최근 용이한 이동성등의 장점으로 기존의 유선랜을 대체하고 있는 무선랜은 AP(Access Point)와 단말기 사이의 보안상 많은 취약성을 갖고 있다. 예를 들어, 동일한 AP에 접속한 공격자에 의해 스니핑된 패킷에서 원본 데이터를 추출 할 수 있는 문제점이 제기되었다. 본 논문에서는 무선랜 환경에서 세밀한 보안이 요구되는 서버/클라이언트 통신 시 스니핑에 의한 원본 데이터의 유출을 방지하여, 안전한 서버/클라이언트 통신이 가능한 보안 통신모듈을 설계하였다. 이 모듈을 사용할 경우 스니핑에 의해 패킷 데이터가 유출되어도 키 없이는 원본 데이터의 내용을 볼 수 없는 장점이 있다.