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Träfflista för sökning "WFRF:(Agrell Erik 1965 ) "

Sökning: WFRF:(Agrell Erik 1965 )

  • Resultat 151-160 av 332
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151.
  • Häger, Christian, 1986, et al. (författare)
  • A Deterministic Construction and Density Evolution Analysis for Generalized Product Codes
  • 2016
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Generalized product codes (GPCs) are extensions of product codes (PCs) where code symbols are protected by two component codes but not necessarily arranged in a rectangular array. In this tutorial paper, we review a deterministic construction for GPCs that has been previously proposed by the authors together with an accompanying density evolution (DE) analysis. The DE analysis characterizes the asymptotic performance of the resulting GPCs under iterative bounded-distance decoding of the component codes over the binary erasure channel. As an application, we discuss the analysis and design of three different classes of GPCs: spatially-coupled PCs, symmetric GPCs, and GPCs based on component code mixtures.
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152.
  • Häger, Christian, 1986, et al. (författare)
  • A Low-Complexity Detector for Memoryless Polarization-Multiplexed Fiber-Optical Channels
  • 2014
  • Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798. ; 18:2, s. 368-371
  • Tidskriftsartikel (refereegranskat)abstract
    • A low-complexity detector is introduced for polarization-multiplexed M-ary phase shift keying modulation in a fiber-optical channel impaired by nonlinear phase noise, generalizing a previous result by Lau and Kahn for single-polarization signals. The proposed detector uses phase compensation based on both received signal amplitudes in conjunction with simple straight-line rather than four-dimensional maximum-likelihood decision boundaries.
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153.
  • Häger, Christian, 1986, et al. (författare)
  • Comparison of Terminated and Tailbiting Spatially Coupled LDPC Codes With Optimized Bit Mapping for PM-64-QAM
  • 2014
  • Ingår i: 2014 European Conference on Optical Communication, ECOC 2014; Cannes; France; 21 September 2014 through 25 September 2014. - 9782954944401 ; , s. Art. no. 6964047-
  • Konferensbidrag (refereegranskat)abstract
    • We optimize the allocation of coded bits to modulation bits for spatially coupled low-density parity-check (SC-LDPC) codes and PM-64-QAM. Tailbiting SC-LDPC codes are shown to offer a similar gap to capacity as their terminated counterparts, at a lower FEC overhead.
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154.
  • Häger, Christian, 1986, et al. (författare)
  • Constellation Optimization for Coherent Optical Channels Distorted by Nonlinear Phase Noise
  • 2012
  • Ingår i: 2012 IEEE Global Communications Conference (GLOBECOM). - 9780819484963 ; , s. 2870-2875
  • Konferensbidrag (refereegranskat)abstract
    • We consider the design of amplitude phase-shift keying (APSK) constellations, targeting their application to coherent fiber-optical communications. Phase compensation is used at the receiver to combat nonlinear phase noise caused by the Kerr-effect. We derive the probability density function of the post- compensated observation for multilevel constellations. Optimal APSK constellations in terms of symbol error probability (SEP) are found assuming a two-stage detector. Performance gains of 3.2 dB can be achieved compared to 16-QAM at a SEP of 10^−2. We optimize the number of rings, the number of points per ring, as well as the radius distribution of the constellation. For low to moderate nonlinearities, radius optimization only yields minor improvements over an equidistant spacing of rings. In the highly nonlinear regime, however, a smaller SEP can be achieved by “sacrificing” the outer ring of the constellation, in favor of achieving good SEP in the remaining rings.
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155.
  • Häger, Christian, 1986, et al. (författare)
  • Data-Driven Estimation of Capacity Upper Bounds
  • 2022
  • Ingår i: IEEE Communications Letters. - 1558-2558 .- 1089-7798.
  • Tidskriftsartikel (refereegranskat)abstract
    • We consider the problem of estimating an upper bound on the capacity of a memoryless channel with unknown channel law and continuous output alphabet. A novel data-driven algorithm is proposed that exploits the dual representation of capacity where the maximization over the input distribution is replaced with a minimization over a reference distribution on the channel output. To efficiently compute the required divergence maximization between the conditional channel and the reference distribution, we use a modified mutual information neural estimator that takes the channel input as an additional parameter. We numerically evaluate our approach on different memoryless channels and show empirically that the estimated upper bounds closely converge either to the channel capacity or to best-known lower bounds.
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156.
  • Häger, Christian, 1986, et al. (författare)
  • Design of APSK Constellations for Coherent Optical Channels with Nonlinear Phase Noise
  • 2013
  • Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 61:8, s. 3362-3373
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the design of amplitude phase-shift keying (APSK) constellations for a coherent fiber-optical communication system where nonlinear phase noise (NLPN) is the main system impairment. APSK constellations can be regarded as a union of phase-shift keying (PSK) signal sets with different amplitude levels. A practical two-stage (TS) detection scheme is analyzed, which performs close to optimal detection for high enough input power. We optimize APSK constellations with 4, 8, and 16 points in terms of symbol error probability (SEP) under TS detection for several combinations of input power and fiber length. For 16 points, performance gains of 3.2 dB can be achieved at a SEP of 10^−2 compared to 16-QAM by choosing an optimized APSK constellation. We also demonstrate that in the presence of severe nonlinear distortions, it may become beneficial to sacrifice a constellation point or an entire constellation ring to reduce the average SEP. Finally, we discuss the problem of selecting a good binary labeling for the found constellations.
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157.
  • Häger, Christian, 1986, et al. (författare)
  • Improving soft FEC performance for higher-order modulations via optimized bit channel mappings
  • 2014
  • Ingår i: Optics Express. - 1094-4087 .- 1094-4087. ; 22:12, s. 14544-14558
  • Tidskriftsartikel (refereegranskat)abstract
    • Soft forward error correction with higher-order modulations is often implemented in practice via the pragmatic bit-interleaved coded modulation paradigm, where a single binary code is mapped to a nonbinary modulation. In this paper, we study the optimization of the mapping of the coded bits to the modulation bits for a polarization-multiplexed fiber-optical system without optical inline dispersion compensation. Our focus is on protograph-based low-density parity-check (LDPC) codes which allow for an efficient hardware implementation, suitable for high-speed optical communications. The optimization is applied to the AR4JA protograph family, and further extended to protograph-based spatially coupled LDPC codes assuming a windowed decoder. Full field simulations via the split-step Fourier method are used to verify the analysis. The results show performance gains of up to 0.25 dB, which translate into a possible extension of the transmission reach by roughly up to 8%, without significantly increasing the system complexity.
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158.
  • Häger, Christian, 1986, et al. (författare)
  • On Parameter Optimization for Staircase Codes
  • 2015
  • Ingår i: Proc. Optical Fiber Communication Conference and Exposition (OFC). - 9781557529374
  • Konferensbidrag (refereegranskat)abstract
    • We discuss the optimization of staircase code parameters based on density evolution. An extension of the original code construction is proposed, leading to codes with steeper waterfall performance.
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159.
  • Häger, Christian, 1986, et al. (författare)
  • Optimized Bit Mappings for Spatially Coupled LDPC Codes over Parallel Binary Erasure Channels
  • 2014
  • Ingår i: Proc. 1st IEEE International Conference on Communications (ICC). - 9781479920037 ; , s. 2064-2069
  • Konferensbidrag (refereegranskat)abstract
    • In many practical communication systems, one binary encoder/decoder pair is used to communicate over a set of parallel channels. Examples of this setup include multi-carrier transmission, rate-compatible puncturing of turbo-like codes, and bit-interleaved coded modulation (BICM). A bit mapper is commonly employed to determine how the coded bits are allocated to the channels. In this paper, we study spatially coupled low-density parity check codes over parallel channels and optimize the bit mapper using BICM as the driving example. For simplicity, the parallel bit channels that arise in BICM are replaced by independent binary erasure channels (BECs). For two parallel BECs modeled according to a 4-PAM constellation labeled by the binary reflected Gray code, the optimization results show that the decoding threshold can be improved over a uniform random bit mapper, or, alternatively, the spatial chain length of the code can be reduced for a given gap to capacity. It is also shown that for rate-loss free, circular (tail-biting) ensembles, a decoding wave effect can be initiated using only an optimized bit mapper.
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160.
  • Häger, Christian, 1986, et al. (författare)
  • Terminated and Tailbiting Spatially-Coupled Codes with Optimized Bit Mappings for Spectrally Efficient Fiber-Optical Systems
  • 2015
  • Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 33:7, s. 1275-1285
  • Tidskriftsartikel (refereegranskat)abstract
    • We study the design of spectrally efficient fiber- optical communication systems based on different spatially cou- pled (SC) forward error correction (FEC) schemes. In particular, we optimize the allocation of the coded bits from the FEC encoder to the modulation bits of the signal constellation. Two SC code classes are considered. The codes in the first class are protograph-based low-density parity-check (LDPC) codes which are decoded using iterative soft-decision decoding. The codes in the second class are generalized LDPC codes which are decoded using iterative hard-decision decoding. For both code classes, the bit allocation is optimized for the terminated and tailbiting SC cases based on a density evolution analysis. An optimized bit allocation can significantly improve the performance of tailbiting SC codes codes over the baseline sequential allocation, up to the point where they have a comparable gap to capacity as their terminated counterparts, at a lower FEC overhead. For the considered terminated SC codes, the optimization only results in marginal performance improvements, suggesting that in this case a sequential allocation is close to optimal.
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  • Resultat 151-160 av 332
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Agrell, Erik, 1965 (332)
Karlsson, Magnus, 19 ... (141)
Wymeersch, Henk, 197 ... (40)
Alvarado, Alex, 1982 (40)
Andrekson, Peter, 19 ... (38)
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Brännström, Fredrik, ... (19)
Yan, Li, 1988 (19)
Karout, Johnny, 1985 (19)
Yoshida, Tsuyoshi, 1 ... (17)
Häger, Christian, 19 ... (16)
Keykhosravi, Kamran, ... (15)
Beygi, Lotfollah, 19 ... (15)
Szczerba, Krzysztof, ... (15)
Graell i Amat, Alexa ... (14)
Eriksson, Tobias, 19 ... (14)
Ström, Erik, 1965 (13)
Sjödin, Martin E, 19 ... (12)
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