• Title/Summary/Keyword: Fading Time

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${\frac{\pi}{4}}$-DQPSK with Nonredundant error correction in Nakagami fading channel (나카가미 페이딩채널에서 비용장 오류정정을 갖는 ${\frac{\pi}{4}}$-DQPSK의 성능분석)

  • 송석일;한영열
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.24 no.12A
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    • pp.1948-1959
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    • 1999
  • The error rate performance of the proposed $\pi$/4-differential quadructure phase shift keying( $\pi$/4-DQPSK) with nonredundant multiple error correction is analyzed for Nakagami fading channel. The scheme for differential detection of $\pi$/4-QPSK with nonredundant multiple error correction utilizes the output that employ the received signal delayed by more than two time slots. It was observed that the performance increased as the error correction capability increased.

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STBC-OFDM Decoding Method for Fast-Fading Channels

  • Lee, Kyu-In;Kim, Jae-Kwon;Cho, Yong-Soo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.32 no.2C
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    • pp.160-165
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    • 2007
  • In this paper, we propose a novel signal detection method that achieves the maximum likelihood (ML) performance but requires much less computational complexity than the ML detection. When the well-known linear decoding method is used for space-time block coded (STBC) OFDM systems in fast-fading channels, co-channel interference (CCI) as well as inter-carrier interference (ICI) occurs. A maximum likelihood (ML) method can be employed to deal with the CCI; however, its computational complexity is very high. In this paper, we propose a signal detection method for orthogonal space-time coded OFDM systems that achieves the similar error performance as the ML method, but requires much less computational complexity.

Outage Performance of Selective Dual-Hop MIMO Relaying with OSTBC and Transmit Antenna Selection in Rayleigh Fading Channels

  • Lee, In-Ho;Choi, Hyun-Ho;Lee, Howon
    • Journal of Information Processing Systems
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    • v.13 no.5
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    • pp.1071-1088
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    • 2017
  • For dual-hop multiple-input multiple-output (MIMO) decode-and-forward relaying systems, we propose a selective relaying scheme that uses orthogonal space-time block code (OSTBC) and transmit antenna selection with maximal-ratio combining (TAS/MRC) or vice versa at the first and second hops, respectively. The aim is to achieve an asymptotically identical performance to the dual-hop relaying system with only TAS/MRC, while requiring lower feedback overhead. In particular, we give the selection criteria based on the antenna configurations and the average channel powers for the first and second hops, assuming Rayleigh fading channels. Also, the numerical results are shown for the outage performance comparison between the dual-hop DF relaying systems with the proposed scheme, only TAS/MRC, and only OSTBC.

Performance of M-ary PPM UWB Radio in Fading Channels

  • Mohammed, Abdel-Hafez;Alagoz, Fatih;Hamalainen, Matti
    • Journal of Communications and Networks
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    • v.5 no.4
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    • pp.365-373
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    • 2003
  • This paper investigates the performance of M-ary pulse position modulation (PPM) multiuser ultra-wideband (UWB) communication systems in terms of symbol error rate (SER) over fading and additive white Gaussian noise (AWGN) channel. Based on Gaussian approximation for the multiple access interference, an expression for the signal-to-noise ratio (SNR) is derived for the UWB system. This expression is used to derive exact SER expressions for coherent UWB receivers. The effect of pulse selection on the SER of multiuser UWB system is studied. In addition to rectangular pulse, the 2nd derivative Gaussian waveform and Rayleigh pulses were considered. We show that the system capacity and/or SER performance can be significantly increased by using the monocycle pulse in fading channels.

Throughput of V-BLAST System using Hybrid ARQ in Correlated Fading Channels (상관된 페이딩 채널에서 하이브리드 ARQ를 사용하는 V-BLAST 시스템의 수율)

  • Kim, Bong-Hoe;Hwang, Seung-Hoon
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.45 no.1
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    • pp.66-71
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    • 2008
  • In this paper, an antenna-switching scheme using negative acknowledgement for hybrid automatic repeat request (H-ARQ) is proposed and analyzed in the Vertical Bell Labs Layered Space-Time(V-BLAST) system, in which the transmit antenna is alternatively switched under retransmission. By analytically evaluating the channel capacity of the proposed scheme over correlated fading channels, it is shown that the adverse effect of the channel correlation is alleviated by the antenna switching scheme. Simulation results demonstrate that the average throughput may be improved in a correlated fading channel without adding much complexity to the process.

Robust Code Acquisition System in Rayleigh Fading Channel (Rayleigh 페이딩 채널에서 강인한 동기 획득 시스템)

  • 장경운;김기채;박용완
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.11 no.5
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    • pp.723-730
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    • 2000
  • In this paper, we perform a performance analysis of serial acquisition scheme using AWGN rejection filter in Rayleigh fading channel and propose robust acquisition scheme using Reference filter, which is utilized to vary threshold at fading rate, in Rayleigh fading channel. AWGN rejection filter is utilized to evaluate running average for compensating channel gain. The JAKE model, which a channel model, is used for the analysis. The simulation result shows that the mean acquisition time of the proposed acquisition system is minimized than acquisition system using AWGN rejection filter and serial-search acquisition system.

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Complexity Reduction Scheme for Lattice Reduction-based MIMO Receiver under Time Varying Fading Environments (시변 페이딩 환경에서 Lattice Reduction 기반 MIMO 수신기를 위한 계산량 감소 기법)

  • Kim, Han-Nah;Choi, Kwon-Hue
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.11A
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    • pp.852-861
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    • 2009
  • We propose a complexity reduced Lattice Reduction(LR) scheme for MIMO detection under time varying fading environments. It is found that for successive MIMO transmission instances, the integer matrix P after LR decomposition remains the same or only a few elements of the matrix P are slightly changed. Based on this feature, we perform LR reduction by setting the initial values for P matrix for the decomposition to be the one obtained in the previous instance not starting from the identity matrix. Simulation results reveal that the proposed scheme drastically reduces overall complexity of LR reduction compared to the conventional scheme for various system parameters under time varying channels. We also show that the proposed scheme can be applied to Seysen LR as well as LLL(Lenstra, Lenstra, and Lavasaz)-LR.

A Simulation Model of Multipath Fading Channels (다중 경로 페이딩 채널의 시뮬레이션 모델)

  • Im, Seung-Gak;Kim, Yun-Seok
    • The Transactions of the Korea Information Processing Society
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    • v.2 no.3
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    • pp.374-381
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    • 1995
  • For designing radio communication systems, radio-channel effects must be considered in order to obtain the desired communication quality, transmitting power, transmission speed and bit error rate. In radio channel, one of major factors that degrade communication quality is multipath fading between transmitting and receiving points. Therefore, a channel model which can describe fading effects correctly is requested. This paper deals with the composition of the channel simulator model that describes multipath fading effects and delay times which occur in the channel. For the performance analysis of the proposed model, trandmitting signal is used in the simulation. From simulation results, it can be shown that probability density function. level crossing rates and average fading-duration time distribution of the faded receive signal are very similar with theoretic values.

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Baseband Signal Compensation Scheme for Frequency Selective Fading Channel and RF Impairments in OFDM System (OFDM 시스템에서 주파수 선택적 페이딩 채널과 RF 불완전 변환 극복을 위한 기저대역 신호보상 기법)

  • Kim, Jae-Kil;Kim, Jeong-Been;Hwang, Jin-Yong;Shin, Dong-Chul;Ahn, Jae-Min
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.1C
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    • pp.55-64
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    • 2010
  • In this paper, we propose a new compensation scheme for combined channel distortions and RF impairments based on the analysis of the impacts of IQ(In-phase/Quadrature) imbalance and phase noise on the OFDM(Orthogonal Frequency Division Multiplexing) system in the direct conversion transceiver and frequency selective fading channel distortion. The proposed scheme estimates the combined distortion by the use of training symbols and the residual distortion by pilot symbols and compensates the combined distortion, including IQ imbalance, phase noise and multipath fading at the same time. The simulation results show that the proposed scheme compensates the combined distortion of IQ imbalance, phase noise and multipath fading simultaneously.

Error rate performance of DS / SSMA system in multipath fading channel (다경로 페이딩 채널에서 DS/SSMA 시스템의 오율특성)

  • 박성경;송왕철;강창언
    • The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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    • v.6 no.1
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    • pp.66-76
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    • 1995
  • In this paper, the error rate performance of DS/SSMA system in multipath fading channel is calculated by computer simulation. At first, the multipath fading channel is modeled with TDL(Tap Delay Line) model. The characteristics of channels, including multipath fading effects and error pattern, are examined by doppler frequency and signal bandwidth, and time spread variation. Using the multipath fading channel model, the error rateperformance of block code and convolutional code is compared, thus the coding sys- tem is applied to the DS / SSMA system. The BER results of DS / SSMA system show that the proposed receiver gives about 2~3[dB] improve- ment compared with the conventional receiver.

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