• ETRI Journal
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• 제31권6호
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• pp.653-659
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• 2009

We have investigated the channel protection layer (PL) effect on the performance of an oxide thin film transistor (TFT) with a staggered top gate ZnO TFT and Al-doped zinc tin oxide (AZTO) TFT. Deposition of an ultra-thin PL on oxide semiconductor films enables TFTs to behave well by protecting the channel from a photo-resist (PR) stripper which removes the depleted surface of the active layer and increases the carrier amount in the channel. In addition, adopting a PL prevents channel contamination from the organic PR and results in high mobility and small subthreshold swings. The PL process plays a critical role in the performance of oxide TFTs. When a plasma process is introduced on the surface of an active layer during the PL process, and as the plasma power is increased, the TFT characteristics degrade, resulting in lower mobility and higher threshold voltage. Therefore, it is very important to form an interface using a minimized plasma process.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권6호
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• pp.1463-1479
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• 2013

In this paper, we propose an unequal protection physical coding sub-layer (PCS) forward error correction (FEC) scheme for efficient and high-quality transmission of video data over optical access networks. Through identifying and resolving the unequal importance of different video frames and passing this importance information from MAC-layer to PCS, FEC scheme of PCS can be adaptive to application-layer data. Meanwhile, we jointly consider the different channel situations of optical network unit (ONU) and improve the efficiency of FEC redundancy by channel adaptation. We develop a theoretical algorithm and a hardware method to achieve efficient FEC assignment for the proposed unequal protection scheme. The theoretical FEC assignment algorithm is to obtain the optimal FEC redundancy allocation vector that results in the optimum performance index, namely frame error rate, based on the identified differential importance and channel situations. The hardware method aims at providing a realistic technical path with negligible hardware cost increment compared with the traditional FEC scheme. From the simulation results, the proposed Channel and Application-layer data Adaptation Unequal Protection (CAAUP) FEC scheme along with the FEC ratio assignment algorithm and the hardware method illustrates the ability of efficient and high-quality transmission of video data against the random errors in the channel of optical access networks.

• 한국통신학회논문지
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• 제39A권7호
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• pp.398-400
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• 2014

In this letter, we propose a cross-layer technique jointly considering modulation coding schemes (MCSs) of medium access control (MAC) layer, source significance information (SSI) and error concealment unit of application (APP) layer, and channel quality information (CQI) of physical (PHY) layer. We demonstrate the improved video quality by the proposed technique when H.264 videos are streamed over Rayleigh fading wireless channels.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2004년도 춘계학술발표대회
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• pp.157-160
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• 2004

본 논문은 미국 차세대 디지털 케이블 방송 표준 규격인 오픈케이블($OpenCable^{TM}$)의 수신제한 모듈인 CableCard의 Physical Layer를 SystemC의 TLM(Transaction Level Modeling)과 RTL(Register-Transfer Level) 모델링 기법으로 설계하였다. 본 논문에서 설계한 CableCard의 Physical Layer는 PCMCIA Interface, Command Inteface 그리고 MPEG-2 TS Interface 로 구성된다. CableCard가 전원이 인가될 때, 카드 초기화를 위하여 동작하는 PCMCIA 인터페이스는 16 비트 PC 카드 SRAM 타입으로 2MByte Memory와 100ns access time으로 동작할 수 있게 설계하였다. PCMCIA 카드 초기화 동작이 완료된 후, CableCard의 기능을 수행하기 위하여 두 개의 논리적 인터페이스가 정의되는데 하나는 MPEG-2 TS 인터페이스이고, 다른 하나는 호스트(셋톱박스)와 모듈 사이의 명령어들을 전달하는 명령어 인터페이스(Command Interface)이다. 명령어 인터페이스(Command Interface)는 셋톱박스의 CPU와 통신하기 위한 1KByte의 Data Channel과 OOB(Out-Of-Band) 통신을 위한 4KByte의 Extended Channel 로 구성되고, 최대 20Mbits/s까지 동작한다. 그리고 MPEG-2 TS는 100Mbits/s까지 동작을 수행할 수 있게 설계하였다. 설계한 코드를 실행한 후, Cadence사의 SimVision을 통해서 타이밍 시뮬레이션을 검증하였다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1995년도 학술대회
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• pp.97-100
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• 1995

In transmission of image sequences over ATM networks, the packet loss problem and channel sharing efficiency are important. As a possible solution two-layer video coding methods have been proposed. These methods transmit video information over the network with different levels of protection with respect to packets loss. In this paper, a two-layer coding method using pyramid structure is proposed and several realizations of two-layer video coding methods are presented and their performances are compared.

• International Journal of Computer Science & Network Security
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• 제21권3호
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• pp.48-54
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• 2021

Security is an important issue for wireless communications and poses many challenges. Most security schemes have been applied to the upper layers of communications networks. Since in a typical wireless communication, transmission of data is over the air, third party receiver(s) may have easy access to the transmitted data. This work examines a new security technique at the physical layer for the sake of enhancing the protection of wireless communications against eavesdroppers. We examine the issue of secret communication through Rayleigh fading channel in the presence of an eavesdropper in which the transmitter knows the channel state information of both the main and eavesdropper channel. Then, we analyze the capacity of the main channel and eavesdropper channel we also analyze for the symbol error rate of the main channel, and the outage probability is obtained for the main transmission. This work elucidate that the proposed security technique can safely complement other Security approaches implemented in the upper layers of the communication network. Lastly, we implement the results in Mat lab

• Journal of information and communication convergence engineering
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• 제14권4호
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• pp.240-245
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• 2016

Scalable video streaming over wireless networks has many challenges. The most significant challenge is related to packet loss. To overcome this problem, in this paper, we propose an unequal loss protection (ULP) method using a new forward error correction (FEC) mechanism for robust scalable video streaming over wireless networks. For an efficient FEC assignment considering video quality, we first introduce a simple and efficient performance metric, the layer-based recovery rate (LRR), for quantifying the unequal error propagation effects of the temporal and quality layers on the basis of packet losses. LRR is based on the unequal importance in both the temporal and the quality layers of a hierarchical scalable video coding structure. Then, the proposed ULP-LRR method assigns an appropriate number of FEC packets on the basis of the LRR to protect the video layers against packet lossy network environments. Compared with conventional ULP algorithms, the proposed ULP-LRR algorithm demonstrates a higher performance for various error-prone wireless channel statuses.

• 중소기업융합학회논문지
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• 제6권3호
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• pp.49-55
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• 2016

본 논문에서는 다양한 채널 환경과 요구 화질 조건에서 사용자의 QoS(Quality of Service)를 만족시키기 위한 영상 전송 방법에 대하여 제안하였다. SVC(Scalable Video Coding) 전송 기법은 비디오 신호를 중요도를 고려한 계층별 신호로 인코딩하여 전송하기 때문에, 비디오 신호 전송에 있어 효과적인 방법이다. 하지만 다양한 채널 환경에 대해서 적응적으로 다수의 사용자가 요구하는 각각의 성능을 선택적으로 만족시키는 기술에 대한 연구는 미비하다. 이에 본 논문에서는 MC-CDMA기반의 SVC 전송 시스템에서 계층 간 차등 OVSF(Orthogonal Variable Spreading Factor) 코드 할당 기법을 통해 SVC 계층 간 protection order를 보장하고 수신부로부터의 피드백을 통해 MC-CDMA의 sub-block과 각각의 계층 신호에 할당된 OVSF 길이를 조절하여 전송함으로써 다양한 채널 환경에서 각각의 사용자의 전송 환경에 따른 최적의 영상품질을 제공하는 적응 전송 시스템을 제안한다. 모의실험을 통해 제안 시스템의 성능분석을 실시한 결과 BER 성능이 향상되어 사용자의 QoS 만족이 가능함을 확인할 수 있었다.

• Journal of Radiation Protection and Research
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• 제29권1호
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• pp.25-31
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• 2004

Results of EGS4 based calculations to study the spatial resolution of gas detectors are described. The calculations include radial distribution of electrons generated by photons of various energies penetrating into variable thickness of Ar and Xe gas layers. Given a desired spatial resolution, the maximum allowed thickness of gas layer for each energy level is determined. In order to obtain 0.1mm spatial resolution, the maximum thickness for the Ar gas is found to be 2mm for photon energies below 14keV while the optimum energy of photons for Xe gas with the same thickness is about 45keV. The results of calculations performed to compare the number of electrons generated by CsI coated micro-channel plate and the number of electrons generated by the Ar and Xe gas layers are described. The results show that the number of electrons generated by the gases is about 10 times higher than the one generated by CsI coated micro-channel plate. A few sample gray scale images generated by these calculations are included.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권9호
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• pp.2266-2284
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• 2012

Recent studies have indicated that a significant improvement in wireless video throughput can be achieved by Cross Layer Design with Side-information (CLDS) protocols. In this paper, we derive the operational rate of a CLDS protocol operating over a realistic wireless channel. Then, a Rate-Distortion (R-D) empirical model for above-capacity Scalable Video Coding (SVC) is deduced to estimate the loss of video quality incurred under inaccurate rate estimation scenarios. Finally, we develop a novel Unequal Error Protection (UEP) scheme which leverages the characteristics of LDPC codes to reduce the distortion of video quality in case of typically-observed burst wireless errors. The efficacy of the proposed rate adaptation architecture over conventional protocols is demonstrated by realistic video simulations using actual IEEE 802.11b wireless traces.