scholarly journals Hierarchical Distribution Matching for Probabilistic Amplitude Shaping

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 958
Author(s):  
Stella Civelli ◽  
Marco Secondini
Keyword(s):  
Lower Layer ◽  
Minimum Energy ◽  
Single Layer ◽  
Low Complexity ◽  
Design Guidelines ◽  
Constant Composition ◽  
Distribution Matching ◽  
Practical Design ◽  
Rate Loss ◽  
Complexity Increase

Probabilistic amplitude shaping—implemented through a distribution matcher (DM)—is an effective approach to enhance the performance and the flexibility of bandwidth-efficient coded modulations. Different DM structures have been proposed in the literature. Typically, both their performance and their complexity increase with the block length. In this work, we present a hierarchical DM (Hi-DM) approach based on the combination of several DMs of different possible types, which provides the good performance of long DMs with the low complexity of several short DMs. The DMs are organized in layers. Each upper-layer DM encodes information on a sequence of lower-layer DMs, which are used as “virtual symbols”. First, we describe the Hi-DM structure, its properties, and the encoding and decoding procedures. Then, we present three particular Hi-DM configurations, providing some practical design guidelines, and investigating their performance in terms of rate loss and energy loss. Finally, we compare the system performance obtained with the proposed Hi-DM structures and with their single-layer counterparts: a 0.19dB SNR gain is obtained by a two-layer Hi-DM based on constant composition DMs (CCDM) compared to a single-layer CCDM with same complexity; a 0.12dB gain and a significant complexity reduction are obtained by a Hi-DM based on minimum-energy lookup tables compared to a single-layer DM based on enumerative sphere shaping with same memory requirements.

scholarly journals Probabilistic Shaping for Finite Blocklengths: Distribution Matching and Sphere Shaping

Entropy ◽  
2020 ◽  
Vol 22 (5) ◽  
pp. 581
Author(s):  
Yunus Can Gültekin ◽  
Tobias Fehenberger ◽  
Alex Alvarado ◽  
Frans M. J. Willems
Keyword(s):  
Gaussian Noise ◽  
Energy Efficient ◽  
Power Efficiency ◽  
Additive White Gaussian Noise ◽  
Constant Composition ◽  
Composition Distribution ◽  
Awgn Channel ◽  
Distribution Matching ◽  
Simulation Results ◽  
Rate Loss

In this paper, we provide a systematic comparison of distribution matching (DM) and sphere shaping (SpSh) algorithms for short blocklength probabilistic amplitude shaping. For asymptotically large blocklengths, constant composition distribution matching (CCDM) is known to generate the target capacity-achieving distribution. However, as the blocklength decreases, the resulting rate loss diminishes the efficiency of CCDM. We claim that for such short blocklengths over the additive white Gaussian noise (AWGN) channel, the objective of shaping should be reformulated as obtaining the most energy-efficient signal space for a given rate (rather than matching distributions). In light of this interpretation, multiset-partition DM (MPDM) and SpSh are reviewed as energy-efficient shaping techniques. Numerical results show that both have smaller rate losses than CCDM. SpSh—whose sole objective is to maximize the energy efficiency—is shown to have the minimum rate loss amongst all, which is particularly apparent for ultra short blocklengths. We provide simulation results of the end-to-end decoding performance showing that up to 1 dB improvement in power efficiency over uniform signaling can be obtained with MPDM and SpSh at blocklengths around 200. Finally, we present a discussion on the complexity of these algorithms from the perspectives of latency, storage and computations.

The hydraulics of two flowing layers with different densities

1986 ◽  
Vol 163 ◽  
pp. 27-58 ◽  
Author(s):  
Laurence Armi
Keyword(s):  
Lower Layer ◽  
Single Layer ◽  
Critical Conditions ◽  
Hydraulic Jumps ◽  
Flow Configurations ◽  
Pass Through ◽  
Bottom Depth ◽  
Downstream Flow ◽  
Energy Equations ◽  
Simple Flow

This is a theoretical and experimental study of the basic hydraulics of two flowing layers. Unlike single-layer flows, two-layer flows respond quite differently to bottom depth as opposed to width variations. Bottom-depth changes affect the lower layer directly and the upper layer only indirectly. Changes in width can affect both layers. In fact for flows through a contraction control two distinct flow configurations are possible; which one actually occurs depends on the requirements of matching a downstream flow. Two-layer flows can pass through internally critical conditions at other than the narrowest section. When the two layers are flowing in the same direction, the result is a strong coupling between the two layers in the neighbourhood of the control. For contractions a particularly simple flow then exists upstream in which there is no longer any significant interfacial dynamics; downstream in the divergent section the flow remains internally supercritical, causing one of the layers to be rapidly accelerated with a resulting instability at the interface. A brief discussion of internal hydraulic jumps based upon the energy equations as opposed to the more traditional momentum equations is included. Previous uniqueness problems are thereby avoided.

scholarly journals Characteristics of Oceanic Warm Cloud Layers within Multilevel Cloud Systems Derived by Satellite Measurements

Atmosphere ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 465 ◽  
Author(s):  
Yuhao Ding ◽  
Qi Liu ◽  
Ping Lao
Keyword(s):  
Double Layer ◽  
Lower Layer ◽  
Single Layer ◽  
Distribution Patterns ◽  
Radar Data ◽  
Multilayered Structures ◽  
Layer System ◽  
Cloud Systems ◽  
Warm Cloud ◽  
Double Layer System

Low-level warm clouds are a major component in multilayered cloud systems and they are generally hidden from the top-down view of satellites with passive measurements. This study conducts an investigation on oceanic warm clouds embedded in multilayered structures by using spaceborne radar data with fine vertical resolution. The occurrences of warm cloud overlapping and the geometric features of several kinds of warm cloud layers are examined. It is found that there are three main types of cloud systems that involve warm cloud layers, including warm single layer clouds, cold-warm double layer clouds, and warm-warm double layer clouds. The two types of double layer clouds account for 23% and in the double layer occurrences warm-warm double layer subsets contribute about 13%. The global distribution patterns of these three types differ from each other. Single-layer warm clouds and the lower warm clouds in the cold-warm double layer system they have nearly identical geometric parameters, while the upper and lower layer warm clouds in the warm-warm double layer system are distinct from the previous two forms of warm cloud layers. In contrast to the independence of the two cloud layers in cold-warm double layer system, the two kinds of warm cloud layers in the warm-warm double layer system may be coupled. The distance between the two layers in the warm-warm double layer system is weakly dependent on cloud thickness. Given the upper and lower cloud layer with moderate thickness of around 1 km, the cloudless gap reaches its maximum when exceeding 600 m. The cloudless gap decreases in thickness as the two cloud layers become even thinner or thicker.

Design guidelines to achieve minimum energy operation for ultra low voltage tunneling FET logic circuits

2015 ◽  
Vol 54 (4S) ◽  
pp. 04DC04 ◽  
Author(s):  
Hiroshi Fuketa ◽  
Kazuaki Yoshioka ◽  
Koichi Fukuda ◽  
Takahiro Mori ◽  
Hiroyuki Ota ◽  
...  
Keyword(s):  
Low Voltage ◽  
Minimum Energy ◽  
Logic Circuits ◽  
Design Guidelines ◽  
Tunneling Fet

Applying Combined Pinch and Exergy Analysis to Closed-Cycle Gas Turbine System Design

1995 ◽  
Vol 117 (1) ◽  
pp. 47-52 ◽  
Author(s):  
V. R. Dhole ◽  
J. P. Zheng
Keyword(s):  
Power Systems ◽  
Gas Turbine ◽  
Gas Turbines ◽  
Power Plants ◽  
Exergy Analysis ◽  
Energy Savings ◽  
Design Guidelines ◽  
Closed Cycle ◽  
Practical Design ◽  
Pinch Technology

Pinch technology has developed into a powerful tool for thermodynamic analysis of chemical processes and associated utilities, resulting in significant energy savings. Conventional pinch analysis identifies the most economical energy consumption in terms of heat loads and provides practical design guidelines to achieve this. However, in analyzing systems involving heat and power, for example, steam and gas turbines, etc., pure heat load analysis is insufficient. Exergy analysis, on the other hand, provides a tool for heat and power analysis, although at times it does not provide clear practical design guidelines. An appropriate combination of pinch and exergy analysis can provide practical methodology for the analysis of heat and power systems. The methodology has been successfully applied to refrigeration systems. This paper introduces the application of a combined pinch and exergy approach to commercial power plants with a demonstration example of a closed-cycle gas turbine (CCGT) system. Efficiency improvement of about 0.82 percent (50.2 to 51.02 percent) can be obtained by application of the new approach. More importantly, the approach can be used as an analysis and screening tool for the various design improvements and is generally applicable to any commercial power generation facility.

scholarly journals The interaction of waves with horizontal cylinders in two-layer fluids

1995 ◽  
Vol 304 ◽  
pp. 213-229 ◽  
Author(s):  
C. M. Linton ◽  
M. McIver
Keyword(s):  
Lower Layer ◽  
Single Layer ◽  
Wave Theory ◽  
Finite Depth ◽  
Scattering Problems ◽  
Infinite Layer ◽  
Linear Water Wave Theory ◽  
Interaction Of Waves ◽  
Reciprocity Relations ◽  
Horizontal Cylinders

We consider two-dimensional problems based on linear water wave theory concerning the interaction of waves with horizontal cylinders in a fluid consisting of a layer of finite depth bounded above by a free surface and below by an infinite layer of fluid of greater density. For such a situation time-harmonic waves can propagate with two different wavenumbers K and k. In a single-layer fluid there are a number of reciprocity relations that exist connecting the various hydrodynamic quantities that arise. These relations are systematically extended to the two-fluid case. It is shown that for symmetric bodies the solutions to scattering problems where the incident wave has wavenumber K and those where it has wavenumber k are related so that the solution to both can be found by just solving one of them. The particular problems of wave scattering by a horizontal circular cylinder in either the upper or lower layer are then solved using multipole expansions.

Elasto-Plastic Bearing Capacity of Four Types of Single-Layer Reticulated Shell Structures Under Fire Hazards

2015 ◽  
Vol 15 (03) ◽  
pp. 1450051
Author(s):  
Yin Bai ◽  
Lu Yang ◽  
Lingfeng Gong
Keyword(s):  
High Temperature ◽  
Bearing Capacity ◽  
Single Layer ◽  
Critical Factor ◽  
Shell Structures ◽  
Nonuniform Temperature ◽  
Fire Hazards ◽  
Ambient Temperatures ◽  
Practical Design ◽  
Fire Conditions

Single-layer reticulated shells are widely used in spatial structures. One critical factor that has to be considered in the design of reticulated shells is the significant adverse impact of high temperature caused by fire on the structures. In order to study the variation of elasto-plastic bearing capacity under high temperature by fire, four types of single-layer reticulated shells (i.e. K6, Geodesic, Schwedler and Lamella) are investigated under two typical fire conditions (i.e. global nonuniform temperature distribution and local high temperature) by the geometrically and materially nonlinear analysis and statistical methods. Practical design formulae for calculating the elasto-plastic bearing capacity of reticulated shell structures under different fire conditions and ambient temperatures are proposed based on the numerical simulation results.

scholarly journals Three-dimensional water-wave scattering in two-layer fluids

2000 ◽  
Vol 423 ◽  
pp. 155-173 ◽  
Author(s):  
J. R. CADBY ◽  
C. M. LINTON
Keyword(s):  
Water Wave ◽  
Lower Layer ◽  
Three Dimensional ◽  
Single Layer ◽  
Wave Theory ◽  
Finite Depth ◽  
Wave Radiation ◽  
Infinite Layer ◽  
Linear Water Wave Theory ◽  
Submerged Sphere

We consider, using linear water-wave theory, three-dimensional problems concerning the interaction of waves with structures in a fluid which contains a layer of finite depth bounded above by a free surface and below by an infinite layer of fluid of greater density. For such a situation time-harmonic waves can propagate with two different wavenumbers K and k. In a single-layer fluid there are a number of reciprocity relations that exist connecting the various hydrodynamic quantities that arise, and these relations are systematically extended to the two-fluid case. The particular problems of wave radiation and scattering by a submerged sphere in either the upper or lower layer are then solved using multipole expansions.

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