• Proceedings of the Korea Information Processing Society Conference
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• 2016.04a
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• pp.847-850
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• 2016

뇌-컴퓨터 인터페이스(Brain-Computer Interface: BCI) 기술의 중요성 및 활용도가 증대됨으로써 EEG(electroencephalogram: EEG)기반의 사용자 인터페이스에 대한 개발 및 연구가 활발히 진행되고 있다. 그러나 뇌파 발생 훈련이 되어 있지 않은 사용자는 EEG 기반의 사용자 인터페이스를 사용하기가 어렵다. 따라서 본 논문에서는 향후 뇌파 훈련을 위한 시뮬레이터를 개발하고자, 그 전단계로 사용자에게서 공통적으로 정확도가 높게 측정되는 채널 및 특징점을 비교, 분석 하였다. 피험자 3명의 왼손 동작 상상과 오른손 동작 상상으로 발생된 EEG 생체신호로부터 ERD/ERS를 확인하고, 8개의 특징점을 추출하여 SVM 분류 알고리즘을 기반으로 정확도를 측정하였으며, ${\mu}$대역 채널 AF4, F4에서의 특징 MAV에서 가장 우수한 성능을 보였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.04a
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• pp.190-192
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• 2015

Discontinuous Reception 메커니즘은 LTE 시스템에서 고속 트래픽 성취에 뒤따른 이동 단말의 배터리 효율성의 중요도 상승에 따라 3GPP 표준으로 채택된 이용 단말의 비 연결적인 컨트롤 채널수신 확인 기법이다. 본 연구에서는 채널 상황 및 트래픽 특성에 효율적인 DRX 파라미터 설정의 중요성에 대해 확인하기 위해 Ns-3 시뮬레이터를 통해 DRX 활성/비활성 파라미터에 따른 성능을 확인하였으며 실험 결과에 통해 DRX 활성/비활성 파라미터의 비율에 따른 성능 변화를 확인하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2012.04a
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• pp.75-78
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• 2012

본 논문은 무선 메쉬 네트워크의 다중 라디오 인터페이스와 다중 채널을 이용한 효율적인 멀티홉 무선 전송을 위한 네트워크 라우팅에 관해 다룬다. 이를 위한 라우팅 매트릭으로는 각 중간 노드의 대역폭 사용량 정보에 기반한 대역폭 예상 변화량을 사용하여 실제 데이터 전송이 진행될 때 기존 보다 안정적인 전송이 가능하도록 유도한다. 멀티 인터페이스 / 멀티 채널의 수의 제약이 존재하는 현실적인 경우를 고려하여 라우팅 매트릭을 정립하고 라우팅 알고리즘을 설계하였다. NS-2 시뮬레이터를 이용한 시뮬레이션 평가를 통해 트래픽 사용량 정보에 기반한 제안 알고리즘이 기존 MIMC 라우팅 알고리즘보다 개선된 성능을 보여준다.

• Journal of KIISE:Information Networking
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• v.37 no.5
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• pp.374-385
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• 2010

Wireless mesh networks can be deployed for various networks from home networking to last-mile broadband Internet access. Wireless mesh networks are composed of mesh routers and mesh clients. In these networks, static nodes form a multi-hop backbone of a large wireless access network that provides connectivity to end-users' mobile terminals. The network nodes cooperate with each other to relay data traffic to its destinations. In order to increase connectivity and better performance, researchers are getting interested in multi-channel and multi-interface wireless mesh networks. In these networks, non-overlapping multiple frequency channels are used simultaneously to increase the aggregate bandwidth available to end-users. Recently, researches have focused on finding suitable channel assignments for wireless network interfaces, equiped in a mesh node, together with efficient routing to improve overall system throughput in wireless mesh networks. This goal can be achieved by minimize channel interference. Less interference among using channels in a network guarantees more aggregated channel capacity and better connectivity of the networks. In this thesis, we propose interference aware channel assignment and routing algorithms for multi-channel multi-hop wireless mesh networks. We propose Channel Assignment and Routing algorithms using Traffic Profiles(CARTP) and Routing algorithms allowing detour routing(CARTP+2). Finally, we evaluate the performance of proposed algorithms in comparison to results from previous methods using ns-2 simulations. The simulation results show that our proposed algorithms can enhance the overall network performance in wireless mesh networks.

• Journal of KIISE:Information Networking
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• v.41 no.4
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• pp.186-191
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• 2014

Previous work only focuses on a maximization of network coding opportunity since it can reduce the number of packets in network system. However, it can make congestion in a relay node as each source node may transmit each packet with the maximum transmission rate based on the channel qualities. Therefore, in this paper, we propose CmNC (Congestion minimized Network Coding over unreliable wireless links) performing opportunistic network coding to guarantee the network coding gain with the consideration of the congestion and channel qualities. The relay node selects the best network code set based on the objective function for reducing the packet loss and congestion via a dynamic programming. With Qualnet simulations, we show CmNC is better up to 20% than the previous work.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.3
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• pp.216-221
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• 2013

In this paper, wireless channel characteristics of massive MIMO system is analyzed by comparing angular spread, cross polarization discrimination(XPD) and delay spread of dual polarized 4 and 128 transmit array antenna systems, by using 3D rat-tracing simulator, Wireless Insite in microcell environments. The analysis shows that increasing the number of transmit antennas results in the smaller angular spread and delay spread, and the higher value of XPD.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.9 no.3
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• pp.347-358
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• 1998

The possibility of modeling the complex and diversified radio environment using Rician channel has been considered. The signals received in Rician channel have been simulated using the computer simulator. The PDF(Probability Density Function of the Envelope amplitude), PSD(Power Spectral Density), LCR(Level Crossing Rate), ADF(Average Duration of Fades) and BER(Bit Error Rate) of the simulated signal have been compared with those of theory. They were shown to be in good agreement.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.6 s.336
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• pp.53-60
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• 2005

Considerable efforts has been recently devoted to the determination of accurate channel models for the power line environment, both for the indoor and outdoor cases. The common limitation of the known and previously published models is the particular type of approach followed. This paper is concerned with a power line channel characteristic measurement for the more fast and efficiently power line communication experiment. The need arises from the fact that indoor power cables consist of conductors and inductors. A capacitive load simulator is a essential equipment in the power line modem development for indoor power line network. We accomplished a channel data base by the frequency response method about the total 224 capacitor load cases. On the basis of this measurement modeling it is here revealed that the power line communication channel is a more deterministic media.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.11 no.4
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• pp.287-295
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• 1986

In this paper, a SBC(sub-band-coding) is proposed to code a speech signal for a digital mobile radio and a robustness of speech quality of the SBC over the Rayleigh fading channel is investigated via a computer simulation. First the Rayleigh fading channel and 16-ary DPSK receiver models are presentes and verified its validitties by comparing with theoretical values. Three different measures: SNR, LPC distance measure and subjective listening test, were used to evaluate the effects due to the Rayleigh fading channel errors. From the results of computer simulation at BER=$10_{-3}$, $10_{-2}$, 5$ imes$$10_{-2}$, it was found that the speech remained quite intelligible at BER=$10_{-2}$and the link is still usuable even at BER=5$ imes$$10_{-2}$ Thus it was concluded that the SBC can be applicable to the digital mobile radio on the Rayleigh fading channel error in the range of $10_{-4}$~$10_{-2}$ without emplowing any error correction codes.

• KSCI Review
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• v.2 no.1
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• pp.55-67
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• 1995

Recently, it is possible to high speed transmission of the non-voiced data, including voice, data, moving image instead of voice only in the past by changing the communication method to digital form from analog owing to the development of semiconductor and computer technology which for information transmission of the remote point. By doing so, we can get the improvement of the noise effect and low cost but the loss of transmission bandwidth. It is necessary to take some method in oreder to reducing the fading which is propotional to transmission bandwidth during the transmission of radio communication channel, especially. When we design the digital communication system, we must considered to the fading effect in order to determination of the transmitting power, modulation /demodulation method, transmission speed, bit error rate. This paper mainly concerns to the method to the channel simulator which descrives the fading effect during the transmission by computer model and digital filter modeling of the radio fading channel by unsing the transmitting and received signal. By taking the inverse of the characteristic of the modeled filter, it is possible to improvement of the communication system by reducing the distortion and inter-symbol interference which occurs in the channel.