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Sökning: L773:0733 8724

  • Resultat 1-10 av 133
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  • Agrell, Erik, 1965-, et al. (författare)
  • Influence of Behavioral Models on Multiuser Channel Capacity
  • 2015
  • Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 33:17, s. 3507-3515
  • Tidskriftsartikel (refereegranskat)abstract
    • In order to characterize the channel capacity of a wavelength channel in a wavelength-division multiplexed (WDM) system, statistical models are needed for the transmitted signals on the other wavelengths. For example, one could assume that the transmitters for all wavelengths are configured independently of each other, that they use the same signal power, or that they use the same modulation format. In this paper, it is shown that these so-called behavioral models have a profound impact on the single-wavelength achievable information rate. This is demonstrated by establishing, for the first time, upper and lower bounds on the maximum achievable rate under various behavioral models, for a rudimentary WDM channel model.
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4.
  • Ahmed, Jawwad, et al. (författare)
  • A Dynamic Bulk Provisioning Framework for Concurrent Optimization in PCE-Based WDM Networks
  • 2012
  • Ingår i: Journal of Lightwave Technology. - IEEE. - 0733-8724. ; 30:14, s. 2229-2239
  • Tidskriftsartikel (refereegranskat)abstract
    • A centralized network control and management plane, such as the one based on a path computation element (PCE), is highly beneficial in terms of resource optimization in wavelength division multiplexing optical networks. Benefits of centralized provisioning are even more evident when connection requests are provisioned in batches, i.e., they allow a better use of network resources via concurrent optimization. In this study, a dynamic bulk provisioning framework is presented with the objective of optimizing the use of network resources that also presents, as an additional benefit, the ability to yield a reduction of the control plane overhead. The rationale behind the proposed framework is based on a mechanism in which the PCE client is allowed to bundle and simultaneously send multiple labeled switch path (LSP) requests to the PCE where, in turn, several bundles can be concurrently processed together as a single bulk. From the network deployment perspective, a PCE-based network architecture is proposed to practically realize this approach. For dynamic bulk provisioning of optical LSP requests, a time-efficient integer linear programming (ILP) model (LSP BP ILP) is presented to minimize the request blocking, the network resource consumption, and the network congestion. In addition, a heuristic based on a greedy randomized adaptive search procedure (GRASP), namely LSP_BP_GRASP, is also proposed as a scalable alternative. The presented results demonstrate significant advantages of the proposed PCE bulk provisioning framework based on concurrent optimization in terms of reduced blocking probability and control overhead when compared with conventional dynamic connection provisioning approaches processing a single connection request at a time.
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5.
  • Alfredsson, Arni, 1989-, et al. (författare)
  • Joint-Polarization Phase-Noise Estimation and Symbol Detection for Optical Coherent Receivers
  • 2016
  • Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 34:18, s. 4394-4405
  • Tidskriftsartikel (refereegranskat)abstract
    • The problem of optimal symbol detection in the presence of laser phase noise is studied, for uncoded polarization-multiplexed fiber-optic transmission. To this end, the maximum a posteriori (MAP) symbol detector is presented. Specifically, it is emphasized that obtaining phase-noise point estimates, and treating them as the true values of the phase noise, is in general suboptimal. Furthermore, a pilot-based algorithm that approximates the MAP symbol detector is developed, using approaches adopted from the wireless literature. The algorithm performs joint-polarization phase-noise estimation and symbol detection, for arbitrary modulation formats. Through Monte Carlo simulations, the algorithm is compared to existing solutions from the optical communications literature. It is demonstrated that joint-polarization processing can significantly improve upon the single-polarization case, with respect to linewidth tolerance. Finally, it is shown that with less than 3% pilot overhead the algorithm can be used with lasers having up to 6 times larger linewidths than the most well-performing blind algorithms can tolerate.
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7.
  • Alireza, Sheikh, 1989-, et al. (författare)
  • Dispersion Compensation FIR Filter with Improved Robustness to Coefficient Quantization Errors
  • 2016
  • Ingår i: Journal of Lightwave Technology. - 0733-8724.
  • Tidskriftsartikel (refereegranskat)abstract
    • In this paper, we propose a new finite impulse response (FIR) filter for chromatic dispersion compensation which is given in closed form. We identify a relation between the out-of-band gain and the in-band error when the filter is implemented with finite-precision arithmetic. In particular, a large out-of-band gain makes the filter more sensitive to coefficient quantization errors due to finite precision digital signal processing. To improve robustness to coefficient quantization errors, our proposed filter is designed based on confining the out-of-band gain. By means of simulations, we show that our filter outperforms other existing FIR filters. The performance gain improves with increasing modulation order and decreasing number of bits used to represent the filter taps.
8.
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9.
  • Alvarado, Alex, 1982-, et al. (författare)
  • Four-Dimensional Coded Modulation with Bit-Wise Decoders for Future Optical Communications
  • 2015
  • Ingår i: Journal of Lightwave Technology. - 0733-8724. ; 33:10, s. 1993-2003
  • Tidskriftsartikel (refereegranskat)abstract
    • Coded modulation (CM) is the combination of forward error correction (FEC) and multilevel constellations. Coherent optical communication systems result in a four-dimensional (4D) signal space, which naturally leads to 4D-CM transceivers. A practically attractive design paradigm is to use a bit-wise decoder, where the detection process is (suboptimally) separated into two steps: soft-decision demapping followed by binary decoding. In this paper, bit-wise decoders are studied from an information-theoretic viewpoint. 4D constellations with up to 4096 constellation points are considered. Metrics to predict the post-FEC bit-error rate (BER) of bit-wise decoders are analyzed. The mutual information is shown to fail at predicting the post-FEC BER of bit-wise decoders and the so-called generalized mutual information is shown to be a much more robust metric. For the suboptimal scheme under consideration, it is also shown that constellations that transmit and receive information in each polarization and quadrature independently (e.g., PM-QPSK, PM-16QAM, and PM-64QAM) outperform the best 4D constellations designed for uncoded transmission. Theoretical gains are as high as 4 dB, which are then validated via numerical simulations of low-density parity check codes.
10.
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