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Sökning: L773:0018 9448 OR L773:0018 9448 > Guillén i Fàbregas Albert

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1.
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2.
  • Chuang, Allen, et al. (författare)
  • Optimal throughput-diversity-delay tradeoff in MIMO ARQ block-fading channels
  • 2008
  • Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 54:9, s. 3968-3986
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we consider an automatic-repeat-request (ARQ) retransmission protocol signaling over a block-fading multiple-input-multiple-output (MIMO) channel. Unlike previous work, we allow for multiple fading blocks within each transmission (ARQ round), and we constrain the transmitter to fixed rate codes constructed over complex signal constellations. In particular, we examine the general case of average input-power-constrained constellations with a fixed signaling alphabet of finite cardinality. This scenario is a suitable model for practical wireless communications systems employing orthogonal frequency division multiplexing (OFDM) techniques over a MIMO ARQ channel. Two cases of fading dynamics are considered, namely, short-term static fading wherechannel fading gains change randomly for each ARQ round, and long-term static fadingwhere channel fading gains remain constant over all ARQ rounds pertaining to a given message. As our main result, we prove that for the block-fading MIMO ARQ channel with a fixed signaling alphabet satisfying a short-term power constraint, the optimal signal-to-noise ratio (SNR) exponent is given by a modified Singleton bound, relating all the system parameters. To demonstrate the practical significance of the theoretical analysis, we present numerical results showing that practical Singleton-bound-achieving maximum distance separable codes achieve the optimal SNR exponent.
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3.
  • Nguyen, Khoa D., et al. (författare)
  • A tight lower bound to the outage probability of discrete-input block-fading channels
  • 2007
  • Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 53:11, s. 4314-4322
  • Tidskriftsartikel (refereegranskat)abstract
    • In this correspondence, a tight lower hound to the outage probability of discrete-input Nakagami-m block-fading channels is proposed. The approach permits an efficient method for numerical evaluation of the bound, providing an additional tool for system design. The optimal rate-diversity tradeoff for the Nakagami-m, block-fading channel is also derived and a tight upper bound is obtained for the optimal coding gain constant.
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4.
  • Nguyen, Khoa D., et al. (författare)
  • Outage Exponents of Block-Fading Channels With Power Allocation
  • 2010
  • Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 56:5, s. 2373-2381
  • Tidskriftsartikel (refereegranskat)abstract
    • Power allocation is studied for fixed-rate transmission over block-fading channels with arbitrary continuous fading distributions and perfect transmitter and receiver channel state information. Both short-and long-term power constraints for arbitrary input distributions are considered. Optimal power allocation schemes are shown to be direct applications of previous results in the literature. It is shown that the short-and long-term outage exponents for arbitrary input distributions are related through a simple formula. The formula is useful to predict when the delay-limited capacity is positive. Furthermore, this characterization is useful for the design of efficient coding schemes for this relevant channel model.
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  • Resultat 1-4 av 4

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