• Title/Summary/Keyword: Fading Time

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Optimal Throughput of Secondary Users over Two Primary Channels in Cooperative Cognitive Radio Networks

  • Vu, Ha Nguyen;Kong, Hyung-Yun
    • Journal of electromagnetic engineering and science
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    • v.12 no.1
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    • pp.1-7
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    • 2012
  • In this paper, we investigated the throughput of a cognitive radio network where two primary frequency channels (PCs) are sensed and opportunistically accessed by N secondary users. The sharing sensing member (SSM) protocol is introduced to sense both PCs simultaneously. According to the SSM protocol, N SUs (Secondary User) are divided into two groups, which allows for the simultaneous sensing of two PCs. With a frame structure, after determining whether the PCs are idle or active during a sensing slot, the SUs may use the remaining time to transmit their own data. The throughput of the network is formulated as a convex optimization problem. We then evaluated an iterative algorithm to allocate the optimal sensing time, fusion rule and the number of members in each group. The computer simulation and numerical results show that the proposed optimal allocation improves the throughput of the SU under a misdetection constraint to protect the PCs. If not, its initial date of receipt shall be nullified.

Green Cooperative Sensing Scheme in Heterogeneous Networks

  • Shen, Lifei;Liu, Jian;Tan, Xinxin;Wang, Lei
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.12 no.2
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    • pp.550-565
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    • 2018
  • Cognitive radio technology is still the key technology of future mobile communication systems. Previous studies have focused on improving spectrum utilization and less energy consumption. In this paper, we propose an Overhead Reduced Scheme (ORS) for green cooperative spectrum sensing. Compared to traditional cooperative sensing scheme, ORS scheme divides the sensing time into three time slots and selects the best multi-mode user to report decisions. In consideration of reporting channel deviation, we derive closed-form expressions for detection probability and false alarm probability of ORS scheme based on Rayleigh fading channel. Simulation results show that ORS scheme can improve the perception accuracy while reducing the perceived delay and energy consumption in the process of perception, so as to realize the green communication.

Design of ATSC Broadcasting Systems Using the Alamouti Scheme (Alamouti 구조를 이용한 ATSC 방송 시스템 설계)

  • 박성익;정태진;김승원;이수인
    • Journal of Broadcast Engineering
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    • v.9 no.1
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    • pp.32-42
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    • 2004
  • In this paper we apply space-time block code with multiple transmitter/receiver antennas to the Advanced Television Systems Committee (ATSC) terrestrial broadcasting systems. Especially, we apply Aiamouti scheme with two transmitter antennas and multiple receiver antennas to the ATSC broadcasting system. Also. diversity technique with multiple receiver antennas and space-time block code scheme with multiple transmitter/receiver antennas are compared. Our simulation results show that the ATSC broadcasting system with multiple transmitter/receiver antennas has an extremely good performance than the scheme with single transmitter/receiver antenna in the Rayleigh fading channel.

Power allocation for sum capacity enhancement of ARQ systems in time-correlated fading channels (시간 상관 채널에서 ARQ 시스템의 합 채널용량 향상을 위한 전력 할당 기법)

  • Park, Jinhyun;Lee, Jae Hong
    • Proceedings of the Korean Society of Broadcast Engineers Conference
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    • 2011.07a
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    • pp.243-246
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    • 2011
  • 무선통신 환경에서 채널 용량이 증가하면 정해진 전송률에 대한 불능 확률(outage probability)이 감소하며, 따라서 통신의 신뢰도가 향상된다. 본 논문에서는 채널 페이딩에 대한 시간 상관성(time correlation)이 있는 환경에서 ARQ 시스템의 합 채널 용량을 향상시키는 전력 할당(power allocation) 기법에 대해 다룬다. 송신기에서 전송이 시작되기 전의 채널 정보를 수신기의 피드백을 통해 알고 있다고 가정하고, ARQ 의 재전송 시점의 채널의 확률분포를 다루었다. 이 분포를 통해 재전송 시점의 채널을 추정하고, ARQ 의 모든 재전송에 대한 합 채널 용량 최대화를 위한 전력 할당 문제를 공식화하였다. 이 문제에 대한 해를 분석적으로 도출하였으며, 모의실험 결과를 통해 제안된 전력 할당 기법으로 얻는 합 채널용량이 재전송 시 동일한 전송전력을 사용한 기존의 기법보다 증가함을 확인한다.

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STF-OFDM Transmission Scheme via Preceding in Frequency Domain (주파수 영역에서의 사전 부호화를 이용한 STF-OFDM 전송 기법)

  • 박상순;김한경;백흥기
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.29 no.7C
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    • pp.954-961
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    • 2004
  • In this paper, we propose a STF(Space-Time-Frequency) coded OFDM(Orthogonal Frequency Division Multiplexing) transmission scheme as an attractive solution for high bit rate data transmission in a multipath fading environment. The STF-OFDM transmission scheme that we propose in this paper is a simple transmission cheme for achieving frequency diversity gain with low complexity. Using preceding in frequency domain, we obtain frequency diversity gain and improve the SER performance of conventional ST-OFDM. The preceding scheme proposed in this paper is a very simple method that can be encoded and decoded with low complexity.

Block-Mode Lattice Reduction for Low-Complexity MIMO Detection

  • Choi, Kwon-Hue;Kim, Han-Nah;Kim, Soo-Young;Kim, Young-Il
    • ETRI Journal
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    • v.34 no.1
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    • pp.110-113
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    • 2012
  • We propose a very-low-complexity lattice-reduction (LR) algorithm for multi-input multi-output detection in time-varying channels. The proposed scheme reduces the complexity by performing LR in a block-wise manner. The proposed scheme takes advantage of the temporal correlation of the channel matrices in a block and its impact on the lattice transformation matrices during the LR process. From this, the proposed scheme can skip a number of redundant LR processes for consecutive channel matrices and performs a single LR in a block. As the Doppler frequency decreases, the complexity reduction efficiency becomes more significant.

Performance of Receive Diversity UWB Systems with Pulse Amplitude and Position Modulation

  • Kim, Sang-Choon
    • Journal of information and communication convergence engineering
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    • v.8 no.5
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    • pp.498-501
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    • 2010
  • In this paper, we extend ultra-wideband (UWB) single input single output (SISO) systems with a hybrid pulse amplitude and position modulation (PAPM) to single input multiple output (SIMO) systems using receive antenna diversity. The performance of a rake receive diversity combining scheme for UWB SIMO systems with a PAPM is examined in a log-normal multipath fading channel and also compared with that of a time-switched transmit diversity (TSTD) multiple input single output (MISO) system. It is seen that as the number of receive antennas increases, the receive diversity combining system improves the error performance. It is shown that the TSTD UWB MISO systems offer the performance equivalent to the receive diversity combining scheme for SIMO systems.

Finite-Horizon Online Transmission Scheduling on an Energy Harvesting Communication Link with a Discrete Set of Rates

  • Bacinoglu, Baran Tan;Uysal-Biyikoglu, Elif
    • Journal of Communications and Networks
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    • v.16 no.3
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    • pp.293-300
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    • 2014
  • As energy harvesting communication systems emerge, there is a need for transmission schemes that dynamically adapt to the energy harvesting process. In this paper, after exhibiting a finite-horizon online throughput-maximizing scheduling problem formulation and the structure of its optimal solution within a dynamic programming formulation, a low complexity online scheduling policy is proposed. The policy exploits the existence of thresholds for choosing rate and power levels as a function of stored energy, harvest state and time until the end of the horizon. The policy, which is based on computing an expected threshold, performs close to optimal on a wide range of example energy harvest patterns. Moreover, it achieves higher throughput values for a given delay, than throughput-optimal online policies developed based on infinite-horizon formulations in recent literature. The solution is extended to include ergodic time-varying (fading) channels, and a corresponding low complexity policy is proposed and evaluated for this case as well.

Performance Analysis of Channel Estimation Schemes for MF Band Digital Radio Broadcasting System (MF 대역 디지털 라디오 방송 시스템을 위한 채널 추정 기법의 성능분석)

  • Song, Jung-Hoon;Kim, Ki-Nam;Roh, Jae-Sung;Cho, Sung-Joon
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.599-603
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    • 2003
  • In this paper, the efficient channel estimationschemes for DRM system(AM band digital radio broadcasting standard) are investigated. In frequency domain, by means of the linear interpolation, the second order interpolation, cubic spline interpolation, and time domain interpolation, the channel impulse response is estimated respectively to compensate the attenuation due to the fading. And in time domain, the frequency channel impulse response is averaged to reduce the attenuation due to the AWGN. By the simulation, the performance of MSE, BER and the complexity of calculation is compared and analysized for each interpolation scheme.

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Dyeing of Pig Skin with Coptis chinensis Franch (황련을 이용한 돈피 염색에 관한 연구)

  • Cho, Sung-Kyo
    • Journal of the Korean Home Economics Association
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    • v.47 no.1
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    • pp.85-91
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    • 2009
  • Dyeability and antimicrobial property of dyed pig skin with Coptis chinensis Franch was investigated. Dyestuff was extracted with water and concentrated. Pig skin was dyed and mordanted according to various dyeing temperature, dyeing time, dyestuff concentration, mordanting methods and kinds of mordants. The results of this experiment were as follows: 1. Dyeability of pig skin with Coptis chinensis Franch was best at 200%(owf) dyestuff concentration, 50${^{\circ}C}$ dyeing temperature, and 20min. dyeing time. 2. Pre-mordanting by Cu improved the K/S values of dyed pig skin. 3. Surface color and color difference of dyed pig skin showed various results according to the mordants used : generally their color was yellow, Al post-mordanted pig skin showed the greatest color difference. 4. Color fastness to drycleaning was considerably high in case of staining compared to fading. Fastness to light was improved by Cu-mordanting while other treatments were not effective. 5. Antimicrobial property of samples was not different (99.9%) between untreated and treated.