• Journal of Satellite, Information and Communications
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• v.12 no.3
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• pp.98-102
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• 2017

In this paper, we study RF-powered backscatter cognitive radio networks to improve the performance for the secondary user which is backscatter radio based wireless sensors. In our proposed model, we consider an avoiding the doubly round-trip attenuation to add a carrier emitter and utilization of spectrum sensing information. When the primary channel is busy, the secondary user is able to harvest RF energy from the channel through a hybrid-access point (H-AP) and a carrier emitter. When the channel becomes idle, the secondary user will be use the harvested energy to operate wireless sensors, to use the sensing and to backscatter through the carrier emitter. We model mathematically the deterministic and multisource elements of a number of tagged channels. In the proposed communication environment, we show the BER performance of the backscatter communication using WiFi signal.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.47 no.6
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• pp.66-74
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• 2010

Recently distributed video coding (DVC) is spotlighted for the environment which has restriction in computing resource at encoder. Wyner-Ziv (WZ) coding is a representative scheme of DVC. The WZ encoder independently encodes key frame and WZ frame respectively by conventional intra coding and channel code. WZ decoder generates side information from reconstructed two key frames (t-1, t+1) based on temporal correlation. The side information is regarded as a noisy version of original WZ frame. Virtual channel noise can be removed by channel decoding process. So the performance of WZ coding greatly depends on the performance of channel code. Among existing channel codes, Turbo code and LDPC code have the most powerful error correction capability. These channel codes use stochastically iterative decoding process. However the iterative decoding process is quite time-consuming, so complexity of WZ decoder is considerably increased. Analysis of the complexity of LPDCA with real video data shows that the portion of complexity of LDPCA decoding is higher than 60% in total WZ decoding complexity. Using the HDA (Hard Decision Aided) method proposed in channel code area, channel decoding complexity can be much reduced. But considerable RD performance loss is possible according to different thresholds and its proper value is different for each sequence. In this paper, we propose an adaptive HDA method which sets up a proper threshold according to sequence. The proposed method shows about 62% and 32% of time saving, respectively in LDPCA and WZ decoding process, while RD performance is not that decreased.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.7
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• pp.720-728
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• 2011

In this paper, development of the monopulse secondary surveillance radar antenna which can be used for IFF system is presented. This antenna that is passive linear array is comprised of the row-feeder and several array-elements. The row-feeder provides sum, different and SLS(Sidelobe Supression) channels which are optimized the distribution of the power and phase ratio. The azimuthe sidelobe level of the sum channel beam pattern is -20 dBc or less. The SLS channel covers the sidelobe of the sum-chanel in the whole azimuth angle range. And the difference channel is used to perform the mono-pulse function, improves the detection accuracy in the azimuth direction. Meanwhile, the arrayelement makes shaped beam in the elevation angle, in order to eliminate the clutter and multipath effects from the ground. Performance of the antenna developed is verified by the measurement of S-parameters and far-field beam pattern, and satisfies all of the development specifications well.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.492-495
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• 2013

최근 자동차의 수요의 증가로 인해 사용자의 편의 및 안전에 대한 요구와 의존도가 증가함에 따라 운전자를 위한 보조 시스템이 구축되고 있다. 현재 운전자를 위한 보조 시스템으로 AVM(Around View Monitoring) 기술이 개발 되었다. 본 논문에서는 운전자가 차량외부의 상황을 실시간으로 인식할 수 있게 하는 AVM(Around View Monitoring) 기술을 조금 더 실용적이고 편의성 있게 사용할 수 있도록 하는 사용자 인터페이스를 제안한다. 이를 위해 영상이 보이는 화면에 다양한 버튼들을 구현하였으며, 화면상에 보이는 버튼에 따라서 4채널 영상과 4채널 영상을 하나로 정합되어 보여주는 영상 그리고 원본영상과 왜곡영상을 따로 보여주는 다양한 인터페이스를 버튼 식으로 구현하여 운전자가 원하는 영상을 상황에 맞게 제공한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.550-552
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• 2002

표준 비디오 압축 기법은 프레임 간의 시간적, 공간적 중복성을 이용하여 데이터를 압축한다. 압축된 프레임이 인터넷을 통하여 전송되는 중에 네트워크의 상태에 따라 패킷의 손실이 발생할 수 있다. 이러한 오류가 발생하면 손실된 블록을 포함하는 프레임의 화질 뿐 아니라, 이 프레임을 참조하여 압축된 이후의 프레임에도 영향을 미친다. 본 논문에서는 전송오류가 발생한 경우, 디코더에서의 오류전파를 최소화하기 위해 보조 모션벡터를 이용한 압축 기법을 제안한다. 즉, 여러 개의 후보 프레임 중 현재 압축하려는 매크로블록과 가장 가까운 값을 가진 두 개의 매크로 블록을 선택하여 그 위치를 기본 모션벡터와 보조 모션벡터로 지정한다. 이때, 두 모션벡터는 서로 다른 프레임에 속한다. 디코더에서 압축해제를 위해 참조하는 기본 모션벡터의 프레임이 손실된 경우, 보조모션 벡터를 이용하여 원래의 화질에 가깝게 디코딩 할 수 있다. 이 기법은 오류제어를 위한 피드백 채널이 필요하지 않으며, 네트워크상의 전송오류 발생시 표준 H.263 압축보다 높은 성능을 보인다.

• Proceedings of the Optical Society of Korea Conference
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• 2000.02a
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• pp.138-139
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• 2000

최근 광섬유의 전송 용량을 효율적으로 극대화하기 위한 방안으로서 파장 분할 다중화 (WDM: Wavelength Division Multiplexing) 방식의 광통신 시스템이 제안되어 사용되고 있다. WDM 시스템에서는 각 채널 (channel) 마다 각기 다른 파장의 광신호가 할당되어 있기 때문에, 여러 파장이 다중화된 광신호에서 원하는 파장의 광신호를 선택하기 위해서는 파장 선택 필터 (wavelength selective filter) 가 필요하다. 격자 보조 동방향 결합기 (GACC: Grating-Assisted Codirectional Coupler) 는 전파 상수(propagation constant) 가 서로 다른 두 도파로 사이에서의 광파워 교환이 파장에 의존하는 특성을 가지고 있기 때문에 WDM 시스템에 응용될 파장 선택 필터로서 많은 연구가 되어 왔다$^{(1),(2)}$ . (중략)

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.46 no.4
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• pp.58-66
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• 2009

Recently the emerging demands of the light-video encoder promotes lots of research efforts on DVC (Distributed Video Coding). As an appropriate video compression method, DVC has been studied, and Wyner-Ziv (WZ) video compression is its one representative structure. The WZ encoder splits the image into two kinds of frames, one is key frame which is compressed by conventional intra coding, and the other is WZ frame which is encoded by WZ coding. The WZ decoder decodes the key frame first, and estimates the WZ frame using temporal correlation between key frames. Estimated WZ frame (Side Information) cannot be the same as the original WZ frame due to the absence of the WZ frame information at decoder. As a result, the difference between the estimated and original WZ frames are regarded as virtual channel noise. The WZ frame is reconstructed by removing noise in side information. Therefore precise noise estimation produces good performance gain in WZ video compression by improving error correcting capability by channel code. But noise cannot be estimated precisely at WZ decoder unless there is good WZ frame information, and generally it is estimated from the difference of corresponding key frames. Also the estimated noise is limited by comparing with frame level noise to reduce the uncertainty of the estimation method. However these methods cannot provide good noise estimation for every frame or each bit plane. In this paper, we propose a noise nodel selection method which chooses a better noise model for each bit plane after generating candidate noise models. Experimental result shows PSNR gain up to 0.8 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1663-1670
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• 2014

Recently, lots of research works have been actively focused on the DVC (Distributed Video Coding) techniques which provide a theoretical basis for the implementation of light video encoder. However, most of these studies have showed poorer performances than the conventional standard video coding schemes such as MPEG-1/2, MPEG-4, H.264 etc. In order to overcome the performance limits of the conventional approaches, several channel-divided distributed video coding schemes have been designed in such a way that some information are obtained while generating side information at decoder side and then these are provided to the encoder side, resulting in channel-divided video coding scheme. In this paper, the interpolation scheme by weighted sum of multiple motion-compensated interpolation frames is introduced and a new channel-divided DVC scheme is designed to effectively describe noisy channels based on the motion vector and its matching characteristics. Through several simulations, it is shown that the proposed method performs better than the conventional methods at low bit-rate and keeps the reconstructed visual quality constantly.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.5
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• pp.805-814
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• 1994

In this paper, we introduce a new method which is available for analyzing the throughput of the packet radio network by using the auxiliary Markov transient matrix with a failure state and a success state. And we consider the effect of symbol error for the network state(X, R) consisted of the number of transmitting PRU X and receiving PRU R. We examine the packet radio network of a continuous time Markov chain model, and the direct sequence binary phase shift keying CDMA radio channel with hard decision Viterbi decoding and bit-by-bit changing spreading code. For the unslotted distributed multi-hop packet radio network, we assume that the packet error due to a symbol error of radio channel has Poisson process, and the time period of an error occurrence is exponentially distributed. Through the throughputs which are found as a function of radio channel parameters, such as the received signal to noise ratio and chips of spreading code per symbol, and of network parameters, such as the number of PRU and offered traffic rate, it is shown that this composite analysis enables us to combine the Markovian packet radio network model with a coded DS/BPSK CDMA radio channel.

• Journal of Broadcast Engineering
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• v.17 no.1
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• pp.179-190
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• 2012

In Distributed Video Coding(DVC), a low complexity encoder can be realized by shifting complex processes of encoder such as motion estimation to decoder. Since not only motion estimation/compensation processes but also channel decoding process needs to be performed at DVC decoder, the complexity of a decoder is significantly increased in consequence. Therefore, various fast channel decoding methods are proposed for the most computationally complex part, which is the channel decoding process in DVC decoding. As the channel decoding process becomes faster using various methods, however, the complexity of the other processes are relatively highlighted. For instance, the complexity of side information generation process in the DVC decoder is relatively increased. In this paper, therefore, a fast method for the DVC decoding is proposed by using adaptive search range method in side information generation process. Experimental results show that the proposed method achieves time saving of about 63% in side information generation process, while its rate distortion performance is degraded only by about 0.17% in BDBR.