• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.265-274
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• 2011

In this paper, it is studied on wide radiating slot antenna's miniaturization for ultra wide-band(UWB) technologies and notch structure to prevent interference between UWB systems and existing wireless systems for using Wi-Fi service of IEEE standards 802.11 a/n. Proposed antenna that wide slot is decreased from $\lambda/2$ to $\lambda/4$ length of resonant frequency has decreased by 72 % compared with conventional antenna. And optimized T-shaped CPW-fed stub has satisfied UWB bandwidth for 3.0~11.8 GHz. Then, creating 2-order Hilbert curve slot line in the stub's patch area, 4.9~5.6 GHz that centered frequency is 5 GHz is eliminated. Finally, the designed antenna constructed on FR4-epoxy has $20{\times}15\;mm^2$ dimension. The measured results that are obtained return loss under -10 dB through 3.2~11.8 GHz without Wi-Fi bandwidth, a linear phase characteristic, a stable group delay, and omnidirectional radiation patterns are presented.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2011.10a
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• pp.255-258
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• 2011

Wi-Fi is a rapidly spreading communications network with Smart phone's publication, the technology has become Ubiquitous-based core network which is connected to personal computers, laptops, and tablet PC. Wi-Fi can send currently a variety of data standard due to developed wireless LAN communications network. One of Wi-Fi standard protocols, which is IEEE 802.11n, use 2.4GHz and 5GHz band. 2.4GHz band is used for 802.11b/g protocol because wavelength is long, diffraction and receiving distance is enough to connect other device. 5GHz band has more available channels to use than 2.4GHz band, so there is no frequency interference of other wireless device such as Bluetooth, RFID. Moreover, there is low interference between channels due to small users in each bandwidth level. In the thesis, we are going to analyze 802.11a/b/g protocol which has used since the beginning of Wi-Fi protocol and 802.11n protocol which is used lately. Furthermore, we look into development and direction for standardization of the next generation wireless LANs which are 802.11ac and 802.11ad. In addition, we will consider for the security, vulnerabilities and its countermeasure in Wireless LAN.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2437-2442
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• 2013

OFDM Wi-Fi AP is susceptible to the co-channel interference. As a countermeasure, the insertion of a smart has been addressed. Despite of the guaranteed efficiency, the complexity of the post-FFT algorithm often keeps itself from being selected as the countermeasure. Instead, simply constructed pre-FFT smart antenna of which the algorithm is based on the received signal covariance matrix is commonly used and the mathematical modeling of it has been deployed. Computer simulations evaluating the improved BER characteristics of the proposed pre-FFT using the covariance matrix of channel estimator output have been carried out. It has been demonstrated that channel matrix output based smart antenna is superior to that using received signal covariance matrix.

• Journal of Korea Society of Digital Industry and Information Management
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• v.9 no.4
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• pp.43-49
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• 2013

In this paper, it is designed inverted triangle structural planar monopole antenna with edge and rectangle slot for UWB(Ultra Wide Band) communication (3.1~10.6 GHz) and researched in about 5.8 GHz notch structure to prevent interference between UWB systems and existing wireless systems for using Wi-Fi service. The antenna have broadband property structurally through inverted triangle structural planar monopole which have edge. and rectangle form addition planned notch slot of 1 mm and height 0.1 mm. Monopole and ground of proposed antenna exist on coplanar plane, and excite as CPW. It used FR4 epoxy dielectric substrate of ${\varepsilon}r$=4.4, and the size is $20{\times}20{\times}1.6$ mm dimension. The measured results that are obtained return loss under -10 dB through 3.1~10.6 GHz(7.5 GHz) without Wi-Fi bandwidth and maximum gain of 8.44 dBi at E-plane. Radiation pattern is about the same that of dipole antenna at all frequency. And using notch slot and it will be able to confirm the quality which becomes notch from 5.8 GHz which are a radio LAN frequency range.

• Journal of Satellite, Information and Communications
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• v.8 no.4
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• pp.135-141
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• 2013

Subway in Korea, most of a metropolitan public transport use only worth ten million people a day floating population of wireless communication can be considered HOT SOPT. These three operators' 2G/3G/4G / Wi-Fi / T-DMB frequency and the number of services to co-exist, and the subway train passengers and subway party for operation and management of the communication network is also the co-subway passenger safety and for this service for the effects of mutual interference of whether the verification was necessary. This research and testing different frequency / communication interference between services and testing to determine whether, through the subway authorities and mobile operators in each frequency-specific interaction check and there is no interference to the safety and quality of subway passengers communication services that can be verified as the data was found. The verification methods in the metro area, not just from one region to determine whether the interference with a common verification methods can be applied.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.05a
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• pp.104-107
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• 2014

Nowadays, smart devices such as smart phones, tablets PC, etc... are exchanging messages using WLAN(Wi-Fi) technologies for sending and receiving messages. With the growth of the smart devices users, the WLAN (Wi-Fi) medium communication could be loaded and then the Quality of Service is undesirable. Currently, there are five types of Wireless LAN such as802.11 a / b / g / n / ac supporting the communication between smart devices and the most used it WLAN 802.11n. Unfortunately, if the WLAN 802.11n is being used by a lot of users, there is poor Quality of Service due to the interference. In this paper, we analyze the Quality of Service provided by the 802.11n and compare with the next generation of wireless 802.11ac.

• International Journal of Computer Science & Network Security
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• v.23 no.5
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• pp.172-178
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• 2023

In this paper, performance of autoencoder based OFDM communication systems is compared with IEEE 802.11a Wireless Lan System (Wi-Fi). The proposed autoencoder based OFDM system is composed of the following steps. First, one sub-carrier's transmitter - channel - receiver system is created by autoencoder. Then learning process of the one sub-carrier autoencoder generates constellation map. Secondly, using the plural sub-carrier autoencoder systems, parallel bundle is configured with inserting IFFT and FFT before and after the channel to configure OFDM system. Finally, the receiver part of the OFDM communication system was updated by re-learning process for adapting channel condition such as multipath channel. For performance comparison, IEEE802.11a and the proposed autoencoder based OFDM system are compared. For channel estimation, Wi-Fi uses initial long preamble to measure channel condition. but Autoencoder needs re-learning process to create an equalizer which compensate a distortion caused by the transmission channel. Therefore, this autoencoder based system has basic advantage to the Wi-Fi system. For the comparison of the system, additive random noise and 2-wave and 4-wave multipaths are assumed in the transmission path with no inter-symbol interference. A simulation was performed to compare the conventional type and the autoencoder. As a result of the simulation, the autoencoder properly generated automatic constellations with QPSK, 16QAM, and 64QAM. In the previous simulation, the received data was relearned, thus the performance was poor, but the performance improved by making the initial value of reception a random number. A function equivalent to an equalizer for multipath channels has been realized in OFDM systems. As a future task, there is not include error correction at this time, we plan to make further improvements by incorporating error correction in the future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.3
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• pp.187-194
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• 2012

Vehicular communication networking is one of the most important building blocks of Intelligent Transportation System(ITS). The vehicular communication network is a wireless communication system enabling vehicles to communicate with each other as well as with roadside base stations. Especially, Wi-Fi based vehicle-to-infrastructure(V2I) communication is an emerging solution to improve the safety, traffic efficiency, and comfort of passengers. In this paper, we proposed a new communication hub platform for vehicles, and explained vehicle communication technology in short. Through car simulation results, we show thar our proposed system reduces signaling interference.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.6
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• pp.589-592
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• 2015

In this paper, we suggested a real-time test-bed for analyzing frequency interference between 2.4 GHz unlicensed devices, such as WiFi, Zigbee, etc. Owing to versatile programming capability of Universal Software Radio Peripheral(USRP) and $Labview^{TM}$, frequency interference environments can be easily modeled. Therefore, performance degradation effects due to various parameters of interferer and victim receiver can be analyzed intuitively. For verification, we showed a frequency interference scenario, which consists of IEEE 802.15.4 as a victim and IEEE 802.11b as a interferer. Measured Bit Error Rate(BER) results showed good agreement with theory and simulation results.

• Journal of the Korea Society for Simulation
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• v.25 no.2
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• pp.21-29
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• 2016

Indoor location system has been used Wi-Fi to get a location. After the development of BLE(Bluetooth Low Energy), the interest in the method of a indoor positioning had been move on. It has more advantages than using Wi-Fi. Easy installation, low power consumption, low signal interference and changeable setting(Advertising interval, tx power, etc.). These things can improve efficiency or accuracy in a indoor positioning system. For this reason, recent indoor positioning system uses BLE rather than Wi-Fi. Accordingly, error factors of BLE beacon based indoor positioning should be studying for high accuracy of indoor positioning. In this research, set up few experiment scenarios and keep a close watch on how technological, environmental factor is affecting positioning accuracy. When a application uses largest signal strength to get the indoor location, the mean error of experimental results was decreased compare to using received signal strength in real-time. The result was same when the application applied average and standard deviation to get the indoor location. Changing advertising interval had an effect on the mean error of indoor positioning. Short advertising interval makes the lower mean error than large advertising interval.