SCALABLE AND EFFICIENT IMPLEMENTATIONS OF THE LDPC DECODER USING RECONFIGURABLE MODELS

2006 ◽  
Vol 17 (02) ◽  
pp. 303-322
Author(s):  
SHARAREH BABVEY ◽  
ANU G. BOURGEOIS ◽  
JOSÉ ALBERTO FERNÁNDEZ-ZEPEDA ◽  
STEVEN W. MCLAUGHLIN

In this paper we propose constant-time parallel algorithms for implementing the message-passing decoder of LDPC codes on a two dimensional R-Mesh and an LARPBS. The R-Mesh and LARPBS are dynamically reconfigurable models that provide hardware reuse and flexibility to problem changes. The same hardware can implement the decoder in both probability and logarithm domains over different channels. Moreover, to decode an alternate code, we may simply set up the required connections between the bit-nodes and check-nodes by modifying the initialization phase of the proposed algorithms. No extra wiring or hardware changes are required, as compared to other existing approaches. We illustrate that the R-Mesh and the LARPBS are efficient models for parallel implementation of the decoder in terms of time complexity, flexibility to problem changes and simplicity of routing messages. We also demonstrate that it is possible to optimally scale large block code sizes down to a smaller, available machine size if using an LR-Mesh or HVR-Mesh, two variants of the R-Mesh model.

1997 ◽  
Vol 05 (04) ◽  
pp. 337-353 ◽  
Author(s):  
David P. Lockard ◽  
Philip J. Morris

The long-term objective of the research described in this paper is to use CAA methodology and parallel computers to increase the understanding of broadband blade noise. In a systematic progression towards simulations of completely realistic configurations and conditions, some simplified problems that address the important features of the flow are investigated. A two-dimensional, Euler code, implemented using the message passing library and Fortran 90 on the IBM SP2, is used to perform the calculations. Results are presented for the interaction of a vortical gust and a flat plate.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Kadir Gümüş ◽  
Tobias A. Eriksson ◽  
Masahiro Takeoka ◽  
Mikio Fujiwara ◽  
Masahide Sasaki ◽  
...  

AbstractReconciliation is a key element of continuous-variable quantum key distribution (CV-QKD) protocols, affecting both the complexity and performance of the entire system. During the reconciliation protocol, error correction is typically performed using low-density parity-check (LDPC) codes with a single decoding attempt. In this paper, we propose a modification to a conventional reconciliation protocol used in four-state protocol CV-QKD systems called the multiple decoding attempts (MDA) protocol. MDA uses multiple decoding attempts with LDPC codes, each attempt having fewer decoding iteration than the conventional protocol. Between each decoding attempt we propose to reveal information bits, which effectively lowers the code rate. MDA is shown to outperform the conventional protocol in regards to the secret key rate (SKR). A 10% decrease in frame error rate and an 8.5% increase in SKR are reported in this paper. A simple early termination for the LDPC decoder is also proposed and implemented. With early termination, MDA has decoding complexity similar to the conventional protocol while having an improved SKR.


2019 ◽  
Vol 880 ◽  
pp. 743-763 ◽  
Author(s):  
Géraldine Davis ◽  
Thierry Dauxois ◽  
Timothée Jamin ◽  
Sylvain Joubaud

The current paper presents an experimental study of the energy budget of a two-dimensional internal wave attractor in a trapezoidal domain filled with uniformly stratified fluid. The injected energy flux and the dissipation rate are simultaneously measured from a two-dimensional, two-component, experimental velocity field. The pressure perturbation field needed to quantify the injected energy is determined from the linear inviscid theory. The dissipation rate in the bulk of the domain is directly computed from the measurements, while the energy sink occurring in the boundary layers is estimated using the theoretical expression for the velocity field in the boundary layers, derived recently by Beckebanze et al. (J. Fluid Mech., vol. 841, 2018, pp. 614–635). In the linear regime, we show that the energy budget is closed, in the steady state and also in the transient regime, by taking into account the bulk dissipation and, more importantly, the dissipation in the boundary layers, without any adjustable parameters. The dependence of the different sources on the thickness of the experimental set-up is also discussed. In the nonlinear regime, the analysis is extended by estimating the dissipation due to the secondary waves generated by triadic resonant instabilities, showing the importance of the energy transfer from large scales to small scales. The method tested here on internal wave attractors can be generalized straightforwardly to any quasi-two-dimensional stratified flow.


Author(s):  
Y-T Wang ◽  
R-H Wong ◽  
J-T Lu

As opposed to traditional pneumatic linear actuators, muscle and rotational actuators are newly developed actuators in rotational and specified applications. In the current paper, these actuators are used to set up two-dimensional pneumatic arms, which are used mainly to simulate the excavator's motion. Fuzzy control algorithms are typically applied in pneumatic control systems owing to their non-linearities and ill-defined mathematical model. The self-organizing fuzzy controller, which includes a self-learning mechanism to modify fuzzy rules, is applied in these two-dimensional pneumatic arm control systems. Via a variety of trajectory tracking experiments, the present paper provides comparisons of system characteristics and control performances.


Author(s):  
Sankalita Saha ◽  
Jason Schlessman ◽  
Sebastian Puthenpurayil ◽  
Shuvra S. Bhattacharyya ◽  
Wayne Wolf

2013 ◽  
Vol 21 (1) ◽  
pp. 1-4 ◽  
Author(s):  
Hiroyuki Kishimoto ◽  
Yuya Shinohara ◽  
Yoshio Suzuki ◽  
Akihisa Takeuchi ◽  
Naoto Yagi ◽  
...  

A pinhole-type two-dimensional ultra-small-angle X-ray scattering set-up at a so-called medium-length beamline at SPring-8 is reported. A long sample-to-detector distance, 160.5 m, can be used at this beamline and a small-angle resolution of 0.25 µm−1was thereby achieved at an X-ray energy of 8 keV.


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