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Sökning: WFRF:(Agrell Erik 1965 )

  • Resultat 161-170 av 332
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161.
  • Irukulapati, Naga Vishnukanth, 1987, et al. (författare)
  • Extending Digital Backpropagation to Account for Noise
  • 2013
  • Ingår i: Proc. of 39th European Conference and Exhibition on Optical Communication (ECOC 2013). - : Institution of Engineering and Technology. - 9781849197595 ; :622 CP, s. We.3.C.4-
  • Konferensbidrag (refereegranskat)abstract
    • We propose a maximum a posteriori-based scheme that extends digital backpropagation (DBP) by accounting for the nonlinear signal-noise interaction. With periodic dispersion compensation we find up to 20% reach improvement over DBP. For uncompensated links DBP is close to optimal.
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162.
  • Irukulapati, Naga Vishnukanth, 1987, et al. (författare)
  • Improved Lower Bounds on Mutual Information Accounting for Nonlinear Signal--Noise Interaction
  • 2018
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 36:22, s. 5152-5159
  • Tidskriftsartikel (refereegranskat)abstract
    • In fiber-optic communications, evaluation of mutual information (MI) is still an open issue due to the unavailability of an exact and mathematically tractable channel model. Traditionally, lower bounds on MI are computed by approximating the (original) channel with an auxiliary forward channel. In this paper, lower bounds are computed using an auxiliary backward channel, which has not been previously considered in the context of fiber-optic communications. Distributions obtained through two variations of the stochastic digital backpropagation (SDBP) algorithm are used as auxiliary backward channels and these bounds are compared with bounds obtained through the conventional digital backpropagation (DBP). Through simulations, higher information rates were achieved with SDBP, which can be explained by the ability of SDBP to account for nonlinear signal--noise interactions
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163.
  • Irukulapati, Naga Vishnukanth, 1987, et al. (författare)
  • On Maximum Likelihood Sequence Detectors for Single-channel Coherent Optical Communications
  • 2014
  • Ingår i: 2014 European Conference on Optical Communication, ECOC 2014; Cannes; France; 21 September 2014 through 25 September 2014. - 9782954944401 ; , s. Art. no. 6964134-
  • Konferensbidrag (refereegranskat)abstract
    • Two different detectors that account for the nonlinear signal–noise interaction in a single channel coherent optical link are compared. The results indicate that accounting for the correlation between the samples leads to improved performance over stochastic digital backpropagation.
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164.
  • Irukulapati, Naga Vishnukanth, 1987, et al. (författare)
  • Stochastic Digital Backpropagation
  • 2014
  • Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 62:11, s. 3956-3968
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we propose a novel detector for single-channel long-haul coherent optical communications, termedstochastic digital backpropagation (SDBP), which takes into account noise from the optical amplifiers in addition to handling deterministic linear and nonlinear impairments. We discuss the design approach behind this detector, which is based on the maximum a posteriori (MAP) principle. As closed-form expressions of the MAP detector are not tractable for coherent optical transmission, we employ the framework of Bayesian graphical models, which allows a numerical evaluation of the proposed detector. Through simulations, we observe that by accounting for nonlinear signal–noise interactions, we achieve a significant improvement in system reach with SDBP over digital backpropagation (DBP) for systems with periodic inlineoptical dispersion compensation. In uncompensated links withhigh symbol rates, the performance difference in terms of system reach for SDBP over DBP is small. In the absence of noise, the proposed detector is equivalent to the well-known DBP detector.
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165.
  • Irukulapati, Naga Vishnukanth, 1987, et al. (författare)
  • Stochastic Digital Backpropagation with Residual Memory Compensation
  • 2016
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 34:2, s. 566-572
  • Tidskriftsartikel (refereegranskat)abstract
    • Stochastic digital backpropagation (SDBP) is an extension of digital backpropagation (DBP) and is based on the maximum a posteriori principle. SDBP takes into account noise from the optical amplifiers in addition to handling deterministic linear and nonlinear impairments. The decisions in SDBP are taken on a symbol-by-symbol (SBS) basis, ignoring any residual memory, which may be present due to non-optimal processing in SDBP. In this paper, we extend SDBP to account for memory between symbols. In particular, two different methods are proposed: a Viterbi algorithm (VA) and a decision directed approach. Symbol error rate (SER) for memory-based SDBP is significantly lower than the previously proposed SBS-SDBP. For inline dispersion-managed links, the VA-SDBP has up to 10 and 14 times lower SER than DBP for QPSK and 16-QAM, respectively.
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166.
  • Ivanov, Mikhail, 1986, et al. (författare)
  • General BER Expression for One-Dimensional Constellations
  • 2012
  • Ingår i: 2012 IEEE Global Communications Conference (GLOBECOM). - 1930-529X. - 9781467309219 ; , s. 2162-2167
  • Konferensbidrag (refereegranskat)abstract
    • A novel general ready-to-use bit-error rate (BER) expression for one-dimensional constellations is developed. The BER analysis is performed for bit patterns that form a labeling. The number of patterns for equally spaced M-PAM constellations with different BER is analyzed.
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167.
  • Ivanov, Mikhail, 1986, et al. (författare)
  • On the Asymptotic Performance of Bit-Wise Decoders for Coded Modulation
  • 2014
  • Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 60:5, s. 2796-2804
  • Tidskriftsartikel (refereegranskat)abstract
    • Two decoder structures for coded modulation over the Gaussian channel are studied: the maximum likelihood symbol-wise decoder, and the (suboptimal) bit-wise decoder based on the bit-interleaved coded modulation paradigm. We consider a 16-ary quadrature amplitude constellation labeled with a Gray labeling. It is shown that the asymptotic loss in terms of pairwise error probability, for any two codewords caused by the bit-wise decoder, is bounded by 1.25 dB. The analysis also shows that the asymptotic loss is zero for a wide range of linear codes, including all rate-1/2 convolutional codes.
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168.
  • Ivanov, Mikhail, 1986, et al. (författare)
  • On the Exact BER of Bit-Wise Demodulators for One-Dimensional Constellations
  • 2013
  • Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 61:4, s. 1450-1459
  • Tidskriftsartikel (refereegranskat)abstract
    • The optimal bit-wise demodulator for M-ary pulse amplitude modulation (PAM) over the additive white Gaussian noise channel is analyzed in terms of uncoded bit-error rate (BER). The BER analysis is based on studying the bit patterns that form a labeling. New closed-form BER expressions for 4-PAM with any labeling are developed. Moreover, closed-form BER expressions for 11 out of 23 possible bit patterns for 8-PAM are presented, which enable us to obtain the BER for 8-PAM with some of the most popular labelings, including the binary reflected Gray code and the natural binary code. Numerical results show that, regardless of the labeling, there is no difference between the optimal demodulator and the symbol-wise demodulator for any BER of practical interest (below 0.1).
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169.
  • Ivanov, Mikhail, 1986, et al. (författare)
  • On the Information Loss of the Max-Log Approximation in BICM Systems
  • 2016
  • Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 62:6, s. 3011 - 3025
  • Tidskriftsartikel (refereegranskat)abstract
    • We present a comprehensive study of the information rate loss of the max-log approximation for M-ary pulse-amplitude modulation (PAM) in a bit-interleaved coded modulation (BICM) system. It is widely assumed that the calculation of L-values using the max-log approximation leads to an information loss. We prove that this assumption is correct for all M-PAM constellations and labelings with the exception of a symmetric 4-PAM constellation labeled with a Gray code. We also show that for max-log L-values, the BICM generalized mutual information (GMI), which is an achievable rate for a standard BICM decoder, is too pessimistic. In particular, it is proved that the so-called harmonized GMI, which can be seen as the sum of bit-level GMIs, is achievable without any modifications to the decoder. We then study how bit-level channel symmetrization and mixing affect the MI and the GMI for max-log L-values. Our results show that these operations, which are often used when analyzing BICM systems, preserve the GMI. However, this is not necessarily the case when the MI is considered. Necessary and sufficient conditions under which these operations preserve the MI are provided.
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170.
  • Jiang, Nan, et al. (författare)
  • Stochastic Backpropagation for Coherent Optical Communications
  • 2011
  • Ingår i: European Conference and Exposition on Optical Communications, ECOC. - Washington, D.C. : OSA. - 2162-2701. - 9781557529312 - 9781557529312
  • Konferensbidrag (refereegranskat)abstract
    • We present stochastic backpropagation, a novel maximum a posteriori detection method for coherent optical communication. The proposed detector is shown to outperform conventional backpropagation in a scenario where nonlinear phase noise is the dominant impairment.
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  • Resultat 161-170 av 332
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Agrell, Erik, 1965 (332)
Karlsson, Magnus, 19 ... (141)
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Alvarado, Alex, 1982 (40)
Andrekson, Peter, 19 ... (38)
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Yan, Li, 1988 (19)
Karout, Johnny, 1985 (19)
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Ström, Erik, 1965 (13)
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Lassing, Johan, 1973 (9)
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Svensson, Arne, 1955 (9)
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