• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.3
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• pp.24-30
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• 2015

Wi-Fi STAs in power saving mode described in the Wi-Fi specification can deteriorate the system performance such as throughput, time delay when they receive data frames from a Wi-Fi AP. This problem is caused by data frame reception failure due to the channel state, and it increases re-transmissions. In this paper, we propose a modified power saving mode considering fairness of Wi-Fi system in order to solve the problem. By simulation, we showed that data throughput can be increased without time delay degradation if the proposed method restricting the number of packet transmission attempts and HARQ are used.

• TTA Journal
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• s.104
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• pp.129-136
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• 2006

TTA는 지난 2월 21일, 프랑스 파리에서 개최된 WiMAX 이사회 회의에서 WiMAX 포럼 공인시험소 자격을 획득하였다. 이런 결과를 바탕으로 TTA는 2006년 9월 Mobile WiMAX 시험장비 도입을 시작으로 시험장비 검증과 모의 인증시험을 거쳐 12월부터 Mobile WiMAX 제품에 대한 WiMAX 포럼 공인 인증시험을 실시할 계획이다. 이에 본 고를 통해 현재 진행 중인 Mobile WiMAX 인증시험 개요 및 동향을 소개하고 자 한다. 1) IEEE802.16-2004 : IEEE Standard for Local and Metropolitan Area Networks-Part16: Air Interface for Fixed Wireless Access Systems

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.678-681
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• 2009

WiFi는 무선인터넷 접속(Wireless LAN) 방식의 하나로서 이동성, 설치용이성, 유연성 등으로 인하여 널리 사용되고 있다. 더욱이 기존 다양한 디지털 기기들이 WiFi 기반의 application을 탑재하여 각종 온라인 콘텐츠를 이용할 수 있게 하면서 점차 보편적인 인터넷 접속수단으로서 변모하고 있는 상황이다. WiFi의 편리성으로 인하여 기업, 공공기관, 교육기관 등에서 네트워크 구축에 WiFi를 사용하는데 그 추세가 개인부문에서 기업부문으로 확산되고 있다. 하지만 유선인터넷이 케이블이라는 매체를 통해 연결되어 외부와 차폐된데 비해 WiFi는 주파수를 매개로하기 때문에 네트워크 접근이 용이하며 이로인해 보안이 취약해 질 수 있다는 것이다. 이로 인하여 일명 워드라이빙(war driving)이라 불리는 서비스의 무단사용뿐만 아니라 악의를 가진 네트워크 침입이 가능해져 개인정보나 사유재산이 침해 가능성이 높다고 할 수 있다. 이에 본 연구에서는 해외의 WiFi의 보안관련 법제도를 살펴보고 이로부터 국내 WiFi보안을 위한 대안을 제시하고자 한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.1
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• pp.35-42
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• 2010

Geo-location using a cellular network is a core technology for LBS together with GPS. With preamble symbols broadcasted in each frame, geo-location using WiBro network can be easily implemented. Because the WiBro network has a cellular structure, it is difficult for a mobile station to detect signals from multiple base stations. In order to get user position using trilateration, long integration techniques for sensitivity enhancement should be employed. This paper presents hybrid integration scheme for WiBro network. By analyzing coherent and non-coherent integration loss according to frequency residual and SNR respectively, optimal combination of the hybrid integration is proposed. Simulation results show that the hybrid integration method is profitable in WiBro network when the frequency residual is estimated and compensated accurately.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.5
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• pp.565-573
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• 2016

Wi-Fi Direct standard technology(Wi-Fi Peer to Peer Technical Specifications v1.2, 2010) was designed for allowing peer to peer communication between two or more devices and various products which have been currently manufactured such as smart phone and smart TV have already provided this technical function. In this technology the role of Coordinator in Wi-Fi infrastructure would be matched to GO(Group Owner) which needs relatively high energy resource and computation power due to the high probability for allowing 3rd-party connection, however, the current standard specification would be limited in terms of energy distribution because it has not included a process to determine the role of GO. To address above problem, this paper classified considerable parameters into the general parameters for the physicality of devices and the specific parameters for considering the role position depending on use-case scenario, and proposed a new method called DIVA to help efficiently determining GO role from the member devices of Wi-Fi Direct network. Furthermore the effect of this mechanism was proved via simulation-based experiments.

• Convergence Security Journal
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• v.23 no.1
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• pp.45-54
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• 2023

Recently, with the development of the Internet of Things, research on protocols that can easily connect devices without a UI to the network has been steadily conducted. To this end, the Wi-Fi Alliance announced Wi-Fi Easy Connect, which can connect to a network using a QR code. However, since Wi-Fi Easy Connect requires a large amount of computation for safety, it is difficult to apply to low-power and miniaturized IoT devices. In addition, Wi-Fi Easy Connect considering scalability is designed to operate in a wired environment, but problems such as duplicate encryption occur because it does not consider a security environment like TLS. Therefore, in this paper, we analyze the Wi-Fi Easy Connect protocol and propose a protocol that can operate efficiently in the TLS environment. It was confirmed that the proposed protocol satisfies the existing security requirements and at the same time reduces about 67% of ECC scalar multiplication operations with a large amount of computation.

• The KIPS Transactions:PartC
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• v.18C no.1
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• pp.45-50
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• 2011

Due to advances in wireless communications and portable terminals, any-time, any-where, and any-device Internet access is possible. In particular, Internet access in moving vehicles is an emerging and challenging issue. Even though a variety studies have been conduced for vehicular networks, little attention is paid to vehicular Wi-Fi networks where a Wi-Fi access point (AP) is installed at the vehicle and the AP is connected to an external base station (BS). In this paper, we conduct a measurement study on the uplink and downlink throughput for Internet access in vehicular Wi-Fi networks. We consider diverse network environments: high-speed train, car, and subway. Measurement results demonstrate that current Internet access in vehicular Wi-Fi networks are not satisfactory for interactive multimedia applications. Therefore, in-depth study on resource management in vehicular Wi-Fi networks is strongly required.

• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.269-272
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• 2007

In order to expand cell coverage, increase system capacity, and offer various multimedia service with high throughput in indoor environment, WiBro Access Point(AP) is developed. Home AP is IFA/Omni type and has stack-up structure of channel card and RF board. SOHO AP is designed to support up to 2FA and has remote RF(RRF) structure using UTP method. Inter-operational test with mobile terminal were completed for 3 terminals using web browsing service simultaneously. The performance test results of WiBro AP are as follows: RCE(EVM) value is -34.431 dB for 64-QAM and throughput is up to 6.79 Mbps(DL) and 1.1 Mbps(UL) with 2.5m Line-of-Sight(LOS) condition.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.9
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• pp.3250-3265
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• 2014

Integrated WiMAX and WiFi networks is of great potential for the future due to the wider coverage of WiMAX and the high data transport capacity of WiFi. However, seamless and secure handover (HO) is one of the most challenging issues in this field. In this paper, we present a novel vertical HO authentication scheme with privacy preserving for WiMAX-WiFi heterogeneous networks. Our scheme uses ticket-based and pseudonym-based cryptographic methods to secure HO process and to achieve high efficiency. The formal verification by the AVISPA tool shows that the proposed scheme is secure against various malicious attacks and the simulation result indicates that it outperforms the existing schemes in terms of communication and computation cost.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.2
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• pp.1250-1264
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• 2017

This paper presents the architecture design, implement, experimental validation of a bistatic backscatter wireless communication system in Wi-Fi network. The operating principle is to communicate a tag's data by detecting the power level of the power modulated Wi-Fi packets to be reflected or absorbed by backscatter tag, in interconnecting with Wi-Fi device and Wi-Fi AP. This system is able to provide the identification and sensor data of tag on the internet connectivity without requiring extra device for reading data, because this uses an existing Wi-Fi AP infrastructure. The backscatter tag consists of Wi-Fi energy harvesting part and a backscatter transmitter/a power-detecting receiver part. This tag can operate by harvesting and generating energy from Wi-Fi signal power. Wi-Fi device decodes information of the tag data by recognizing the power level of the backscattered Wi-Fi packets. Wi-Fi device receives the backscattered Wi-Fi packets and generates the tag's data pattern in the time-series of channel state information (CSI) values. We believe that this system can be achieved wireless connectivity for ultra- low-power IoT and wearable device.