• Title, Summary, Keyword: spatial fading correlation

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Analysis on Bi-Directional Use of Spatial Resources (공간 자원의 양방향 활용에 대한 분석)

  • Ju, Hyung-Sik;Lee, Sung-Eun;Hong, Dae-Sik
    • Journal of the Institute of Electronics Engineers of Korea TC
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    • v.48 no.8
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    • pp.36-41
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    • 2011
  • In multiple antenna systems, spatial facing correlation causes a significant degradation in performance. In this work, a method for reducing the sensitivity to spatial fading correlation through the bi-directional use of spatial resources is investigated. Firstly, the concept of bi-directional use of spatial resources is introduced. Then, the ability of this technique to reduce the sensitivity to spatial fading correlation is then shown through an analysis of the number of usable eigenmodes (UEMs). This system is found to efficiently reduce the sensitivity to spatial fading correlation.

New Spatial-Multiplexing Scheme for Erasure Fading Channels (Erasure 페이딩 채널 환경에서 새로운 공간 다중화 기법)

  • Kim, Ho-Jun;Kim, Jun-Ho;Jung, Tae-Jin;Kim, Cheol-Sung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.11A
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    • pp.1045-1050
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    • 2010
  • This paper proposes a new $2{\times}2$ spatial-multiplexing(SM) scheme which is constructed by serially concatenating an orthogonal precoder with a conventional SM. Compared to the conventional SM, the proposed scheme achieves improved performance under erasure fading channels without any performance loss under non-erasure fading channels. Particularly the performance gain is more larger as a correlation value between two receive antennas increases.

Characteristic-Function-Based Analysis of MIMO Systems Applying Macroscopic Selection Diversity in Mobile Communications

  • Jeong, Wun-Cheol;Chung, Jong-Moon;Liu, Dongfang
    • ETRI Journal
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    • v.30 no.3
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    • pp.355-364
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    • 2008
  • Multiple-input multiple-output (MIMO) systems can provide significant increments in capacity; however, the capacity of MIMO systems degrades severely when spatial correlation among multipath channels is present. This paper demonstrates that the influence of shadowing on the channel capacity is more substantial than that of multipath fading; therefore, the shadowing effect is actually the dominant impairment. To overcome the composite fading effects, we propose combining macroscopic selection diversity (MSD) schemes with MIMO technology. To analyze the system performance, the capacity outage expression of MIMO-based MSD (MSD-MIMO) systems using a characteristic function is applied. The analytic results show that there are significant improvements when MSD schemes are applied, even for the two-base-station diversity case. It is also observed that the effect of spatial correlation due to multipath fading is almost negligible when multiple base stations cooperatively participate in the mobile communication topology.

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Improved Code Timing Estimator for DS-CDMA Systems Using Correlated Antennas in Time-Varying Fading Channels (시변 페이딩 채널에서 상관관계가 있는 안테나를 사용하는 DS-CDMA 통신 시스템을 위한 개선된 최대가능도 코드 타이밍 추정기)

  • Kim Sang-Choon;Jeong Bong-Sik
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.5
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    • pp.910-920
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    • 2006
  • We consider the problem of estimating a code-timing of DS-CDMA signal in antenna array systems in the presence of flat fading channels and near-far environments. We derive an approximate maximum likelihood algorithm of estimating the code-timing of a desired user for DS-CDMA systems to better utilize the time-varying characteristics of the fading process. In the development of code timing estimator, the given observation bits are divided into many sets of sub-windows with each sufficiently large. The proposed method uses sub-windows with equal size associated with the coherence time of channel fading. The alternative approach is that without the estimation of the fading rate, the sufficiently given observation bits are simply separated into two consecutive sets of sub-windows. The derivation of the proposed algorithms is based on multiple antennas partially correlated in space. The impacts of spatial fading correlation on acquisition and men acquisition time performance of the proposed algorithms are also examined.

Performance of Doubly Correlated MIMO Channel in OFDM Spatial Multiplexing Systems

  • An, Jin-Young;Park, Hee-Jun;Kim, Sang-Choon
    • Journal of information and communication convergence engineering
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    • v.6 no.4
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    • pp.359-363
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    • 2008
  • In this paper, the capacity of MIMO fading channel in the OFDM-based spatial multiplexing systems is analyzed when there is scattering at both transmitter and receiver. The employed MIMO channel model is spanning from the correlated low-rank case to uncorrelated high-rank case at both transmitter and receiver. The effects of spatial fading correlation on the capacity of MIMO channel is examined when the channel is known and unknown at the transmitter. We also evaluate the impacts of a channel estimation error at the transmitter on the MIMO channel capacity.

MIMO Capacity, Level Crossing Rates and Fades: The Impact of Spatial/Temporal Channel Correlation

  • Giorgetti, Andrea;Smith, Peter J.;Shafi, Mansoor;Chiani, Marco
    • Journal of Communications and Networks
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    • v.5 no.2
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    • pp.104-115
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    • 2003
  • It is well known that Multiple Input Multiple Output (MIMO) systems offer the promise of achieving very high spectrum efficiencies (many tens of bit/s/Hz) in a mobile environment. The gains in MIMO capacity are sensitive to the presence of spatial and temporal correlation introduced by the radio environment. In this paper, we examine how MIMO capacity is influenced by a number of factors e.g., a) temporal correlation b) various combinations of low/high spatial correlations at either end, c) combined spatial and temporal correlations. In all cases, we compare the channel capacity that would be achievable under independent fading. We investigate the behaviour of "capacity fades," examine how often the capacity experiences the fades, develop a method to determine level crossing rates and average fade durations and relate these to antenna numbers. We also evaluate the influence of channel correlation on the capacity autocorrelation and assess the fit of a Gaussian random process to the temporal capacity sequence. Finally we note that the particular spatial correlation structure of the MIMO channel is influenced by a large number of factors. For simplicity, it is desirable to use a single overall correlation measure which parameterizes the effect of correlation on capacity. We verify this single parameter concept by simulating a large number of different spatially correlated channels.

A Comparative Analysis of Orthogonal SIBC Algorithms in Spatially Correlated Rayleigh Fading Environments (공간 코릴레이션이 존재하는 레일리이 페이딩 환경에서 직교 STBC 알고리즘의 성능 비교 분석)

  • Jang, Eun-Kyoung;Park, Hyung-Rae;Kim, Chang-Ju
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.10C
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    • pp.836-843
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    • 2008
  • In this paper we derive the theoretical performance of orthogonal STBC algorithms in spatially correlated Rayleigh fading environments and compare their performances for various correlation conditions. We first derive the theoretical BER of the orthogonal STBC algorithms for both M-ary PSK and M-ary QAM modulation schemes by using the eigenvalues of the channel correlation matrix and then investigate the effect of the spatial correlation on the performance for various transmission rates of $1{\sim}4bps/Hz$. Performance analysis illustrates that the Alamouti scheme provides the better performance than the Tarokh scheme for all the transmission rates in highly correlated fading environments with a correlation being larger than 0.9.

Performance Evaluation of MIMO System by Spatial Correlation in Reverberation Chamber (잔향챔버내에서 공간 상관도에 의한 MIMO 시스템의 성능평가)

  • Kim, Jong-Sung
    • Journal of the Institute of Electronics and Information Engineers
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    • v.51 no.10
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    • pp.26-33
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    • 2014
  • The spatial correlation (SC) for a multipath environment based on a $2{\times}2$ MIMO system are computed on the observation planes in the Rayleigh/Rician fading channels inside a mode stirred chamber. The correlation coefficients were obtained and compared for different distances and orthogonal polarization between two transmit antennas. The proposed method is useful for quantifying the potential diversity gain in antenna diversity systems.

Hybrid Diversity-Beamforming Technique for Outage Probability Minimization in Spatially Correlated Channels

  • Kwon, Ho-Joong;Lee, Byeong-Gi
    • Journal of Communications and Networks
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    • v.9 no.3
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    • pp.274-281
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    • 2007
  • In this paper, we present a hybrid multi-antenna technique that can minimize the outage probability by combining the diversity and beamforming techniques. The hybrid technique clusters the transmission antennas into multiple groups and exploit diversity among different groups and beamforming within each group. We analyze the performance of the resulting hybrid technique for an arbitrary correlation among the transmission antennas. Through the performance analysis, we derive a closed-form expression of the outage probability for the hybrid technique. This enables to optimize the antenna grouping for the given spatial correlation. We show through numerical results that the hybrid technique can balance the trade-offs between diversity and beamforming according to the spatial correlation and that the optimally designed hybrid technique yields a much lower outage probability than the diversity or beamforming technique does in partially correlated fading channels.

Analysis of short-term feding characteristics in urban microcellular environment (도심지 마이크로 셀 환경에서의 단구간 페이딩 특성 분석)

  • 송기홍;김종호;함영권;김제영
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.22 no.8
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    • pp.1652-1658
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    • 1997
  • We analyze the short-term fading characteristics of received signal in urban microcellular environment. In order to analyze the fading signal, we obtain the fading distributions by distance, the received power pattern by arrival angle and the spatial correlation coefficients of fading signal by spacing distance between two antennas. In addition, we compare the distributions of simulated fading signal with the Rician parameter K in various conditions. As the results, it can be seen that the occuring period of deep fade and fade range in microcell are different as the distance between two antennas;besides, the period of fade and fade range in OBS region occur shortly and deeply as compared with those in LOS region. The data used in analysis are obtained by the simulation program using ray tracing technique.

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