• Title/Summary/Keyword: IEEE802.11a

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MAC Address Spoofing Attack Detection and Prevention Mechanism with Access Point based IEEE 802.11 Wireless Network (Access Point 기반 무선 네트워크 환경에서의 MAC Address Spoofing 공격 탐지 및 차단 기법)

  • Jo, Je-Gyeong;Lee, Hyung-Woo
    • Journal of Internet Computing and Services
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    • v.9 no.4
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    • pp.85-96
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    • 2008
  • An authentication procedure on wired and wireless network will be done based on the registration and management process storing both the user's IP address and client device's MAC address information. However, existent MAC address registration/administration mechanisms were weak in MAC Spoofing attack as the attacker can change his/her own MAC address to client's MAC address. Therefore, an advanced mechanism should be proposed to protect the MAC address spoofing attack. But, existing techniques sequentially compare a sequence number on packet with previous one to distinguish the alteration and modification of MAC address. However, they are not sufficient to actively detect and protect the wireless MAC spoofing attack. In this paper, both AirSensor and AP are used in wireless network for collecting the MAC address on wireless packets. And then proposed module is used for detecting and protecting MAC spoofing attack in real time based on MAC Address Lookup table. The proposed mechanism provides enhanced detection/protection performance and it also provides a real time correspondence mechanism on wireless MAC spoofing attack with minimum delay.

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A New Interference-Aware Dynamic Safety Interval Protocol for Vehicular Networks

  • Yoo, Hongseok;Chang, Chu Seock;Kim, Dongkyun
    • Journal of Korea Society of Industrial Information Systems
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    • v.19 no.2
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    • pp.1-13
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    • 2014
  • In IEEE 802.11p/1609-based vehicular networks, vehicles are allowed to exchange safety and control messages only within time periods, called control channel (CCH) interval, which are scheduled periodically. Currently, the length of the CCH interval is set to the fixed value (i.e. 50ms). However, the fixed-length intervals cannot be effective for dynamically changing traffic load. Hence, some protocols have been recently proposed to support variable-length CCH intervals in order to improve channel utilization. In existing protocols, the CCH interval is subdivided into safety and non-safety intervals, and the length of each interval is dynamically adjusted to accommodate the estimated traffic load. However, they do not consider the presence of hidden nodes. Consequently, messages transmitted in each interval are likely to overlap with simultaneous transmissions (i.e. interference) from hidden nodes. Particularly, life-critical safety messages which are exchanged within the safety interval can be unreliably delivered due to such interference, which deteriorates QoS of safety applications such as cooperative collision warning. In this paper, we therefore propose a new interference-aware Dynamic Safety Interval (DSI) protocol. DSI calculates the number of vehicles sharing the channel with the consideration of hidden nodes. The safety interval is derived based on the measured number of vehicles. From simulation study using the ns-2, we verified that DSI outperforms the existing protocols in terms of various metrics such as broadcast delivery ration, collision probability and safety message delay.

Link Adaptive MAC protocol for Wi-Fi (Wi-Fi 네트워크를 위한 매체적응 MAC 프로토콜)

  • Kim, Byung-Seo;Han, Se-Won;Ahn, Hong-Young
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.9 no.3
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    • pp.69-74
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    • 2009
  • A novel protocol is proposed to achieve sub-carner-based rate adaptation in OFDM-based wireless systems. The protocol requires the addition of one OFDM symbol to the Clear-to-Send (CTS) packet defined in the IEEE 802.11 standard_ When receiving a Ready-To-Send (RTS) packet, the receiver determines the number of bits to be allocated in each sub-carrier through channel estimation. This decision is delivered to the sender using an additional OFDM symbol. That is, bit-allocation over sub-carriers is achieved using only one additional OFDM symbol. The protocol also provides an error recovery process to synchronize the bit-allocation information between the sender and receiver. The protocol enhances the channel efficiency in spite of the overhead of one additional OFDM symbol.

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An IPv6 based Fast Handover Deployment Scheme for WiBro Networks (광대역 무선 인터넷 망에서 IPv6 기반의 고속 핸드오버 도입을 위한 방안)

  • Shim, Min-Sik;Kim, Hwa-Sung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.31 no.11A
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    • pp.1101-1112
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    • 2006
  • With the recent growth in demand for high-data rate multimedia services in the wireless environments, the Mobile Broadband Wireless Access (MBWA) technologies, such as WiBro (Wireless Broadband internet) system, are gradually coming into the spotlight. Unlike the conventional mobile communication networks based on cellular system, the WiBro system basically consists of IP based backbone networks that will be ultimately deployed by Ipv6 (IP version six) based backbone networks according to the All-IP trend for the network evolution. In such wireless mobile environments, it is needed to support the mobility management protocol on network layer as well as physical layer and Medium Access Control (MAC) layer in WiBro system. Accordingly, in this paper, we propose a fast handover scheme for improving the handover performance in IPv6 based WiBro system and show that the proposed scheme achieves loss-free and low handover latency during inter-subnet movement of the mobile stations through the simulation.

Development of EM Wave Absorber for Countermeasure against EM Wave Environment of 2.4 GHz Wireless LAN (2.4 GHz 무선LAN 전자파 환경대책용 전파흡수체 개발)

  • Yoon, Sang-Gil;Kim, Dae-Hun;Park, Soo-Hoon;Kim, Dong-Il
    • Journal of Navigation and Port Research
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    • v.33 no.3
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    • pp.193-197
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    • 2009
  • In this paper, the EM wave absorber was designed and fabricated for improvement of Wireless LAN environment at 2.4 GHz. We fabricated several samples in different composition ratios of Sendust and CPE(Chlorinated Polyethylene). Absorption abilities were simulated in accordance with different thicknesses of the prepared absorbers and changed complex relative permittivity and permeability due to composition ratio. The mixing ratio of Sendust and CPE was searched as 80: 20 wt.% by experiments and simulation Then the EM wave absorber was fabricated and tested using the simulated data. As a result, the EM wave absorber was fabricated based on simulated data. Simulated and measured results agreed well. As a result, the developed EM wave absorber with thickness of 3.25 mm has absorption ability of 19 dB at 2.4 GHz.

Design and Implementation of Baseband Modem Receiver for MIMO-OFDM Based WLANs (MIMO-OFDM 기반 무선 LAN 시스템을 위한 기저대역 모뎀 수신부 설계 및 구현)

  • Jang, Soo-Hyun;Roh, Jae-Young;Jung, Yun-Ho
    • Journal of Advanced Navigation Technology
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    • v.14 no.3
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    • pp.328-335
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    • 2010
  • In this paper, an efficient algorithm and area-efficient hardware architecture have been proposed for $2{\times}2$ MIMO-OFDM based WLAN baseband modem with two transmit and two receive antennas. To enhance the performance of the receiver, the efficient timing synchronization algorithm and symbol detector based on MML algorithm are presented. Also, by sharing the hardware block with multi-stage pipeline structure and using the complex multiplier based on polar-coordinate, the complexity of the proposed architecture is dramatically decreased. The proposed area-efficient hardware design was designed in hardware description language (HDL) and synthesized to gate-level circuits using 0.13um CMOS standard cell library. As a result, the complexity of the proposed modem receiver is reduced by 56% over the conventional architecture.

Interference Cancellation for Wireless LAN Systems Using Full Duplex Communications (전이중 통신 방식을 사용하는 무선랜을 위한 간섭 제거 기법)

  • Han, Suyong;Song, Choonggeun;Choi, Jihoon
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.40 no.12
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    • pp.2353-2362
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    • 2015
  • In this paper, we employ the single channel full duplex radio for wireless local area network (WLAN) systems, and design digital interference cancellers using adaptive signal processing. When the full duplex scheme is used for WLAN systems with multiple transmit and receive antennas, some interference is caused through the feedback of transmit signals from multiple antennas. To remove the feedback interference, we derive the least mean square (LMS), normalized LMS (NLMS), and recursive least squares (RLS) algorithms based on adaptive signal processing techniques. In addition, we analyze the theoretical convergence of the proposed LMS and RLS methods. The channel capacity of full duplex radios increases by two times than that of half duplex radios, when the packet error rate (PER) performances for the two systems are identical. Through numerical simulations in WLAN systems, it is shown that the full duplex method with the proposed interference cancellers has a similar PER performance with the conventional half duplex transmission scheme.

TCP Fairness Improvement Scheme using Adaptive Contention Window in Wireless Mesh Networks (무선 메쉬 네트워크에서 적응적 경쟁 윈도우를 이용한 TCP Fairness 개선 방안)

  • Jang, In Sik;Min, Seok Hong;Kim, Bong Gyu;Choi, Hyung Suk;Lee, Jong Sung;Kim, Byung Chul;Lee, Jae Yong
    • Journal of the Korea Institute of Military Science and Technology
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    • v.16 no.3
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    • pp.322-331
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    • 2013
  • Wireless Mesh Networks(WMNs) is generally composed of radio nodes in the mesh topology. WMNs consists of mesh client, mesh router and gateway connected to a wired network. Each client and router relay messages to the gateway for communication. WMNs is widely used recently in many areas can provide extended coverage based on multi-hop communication and ubiquitous communication at any time and any location. However the competition and collision between each node to transmit data is inevitable when the same channel is used for transmission. The transmission opportunities and the throughput of nodes located far from gateway decrease more if the communication channel is accessed based on competitive CSMA/CA scheme using DCF(Distributed Coordination Function) provided by IEEE 802.11 MAC. In this paper, we improve the performance of the TCP fairness and throughput of the nodes with more than 2 hops by applying various algorithms for controlling contention window values. Also, we evaluate the performance using ns-2 simulator, According to the results, proposed scheme can enhance the fairness characteristic of each node irrespective of data to the gateway.

Design of Paper-Based Reconfigurable Frequency Selective Surface for Spectrum Control of Indoor Environments (실내 공간 스펙트럼 제어를 위한 종이기반 재구성 주파수 선택구조 설계)

  • Cho, Sung-Sil;Hong, Ic-Pyo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.41 no.7
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    • pp.775-782
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    • 2016
  • In this paper, we presented the paper-based reconfigurable frequency selective surface(FSS) for transmitting or blocking the wireless LAN signal in indoor environments. The proposed reconfigurable FSS are designed on coated paper using a printing of conductive ink and conductive adhesive for PIN diode, which provides ON/OFF of the reconfigurable FSS for passing or blocking the 5GHz signal. The reconfigurable FSS attached on the wall can pass or block the incident wireless signal as the received signal strength in indoor. To provide the validity of the proposed FSS, we fabricated the reconfigurable FSS on the paper and confirmed the very similar results between simulations and measurements. From the measured results of the proposed spectrum control system, we know that the proposed reconfigurable FSS can block about 20dB at 5.745GHz~5.805GHz.

Conceptual Design of Emergency Communication System to Cope with Severe Accident in Nuclear Power Plants (중대사고를 대비한 원전비상통신시스템 개념설계)

  • Son, Kwang Seop
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.5
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    • pp.58-69
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    • 2014
  • To cope with sever accident like Fukushima accident, the emergency response system is needed. It consist of the hardened I&C system and the mobile control station. The hardened I&C system monitors the state in the nuclear power plant and controls the emergency equipment such as valves, pumps and the mobile control station placed at 30km away from nuclear power plant receives the status information from the hardened I&C system and transmits the control data to the hardened I&C system. In this paper, we design the emergency communication system connecting the hardened I&C system to the mobile control station and analyze the performance of the system. This system consists of the terrestrial communication system and the satellite communication. The performance such as a communication link budget, throughput and delay time is analyzed for each system.