54,435 research outputs found
Probabilistic Shaping for Finite Blocklengths: Distribution Matching and Sphere Shaping
In this paper, we provide for the first time 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. As the blocklength
decreases, however, the resulting rate loss diminishes the efficiency of CCDM.
We claim that for such short blocklengths and over the additive white Gaussian
channel (AWGN), 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),
enumerative sphere shaping (ESS) and shell mapping (SM), are reviewed as
energy-efficient shaping techniques. Numerical results show that MPDM and SpSh
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. 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 perspective of
latency, storage and computations.Comment: 18 pages, 10 figure
Matching the Nagy-Soper parton shower at next-to-leading order
We present an MC@NLO-like matching of next-to-leading order QCD calculations
with the Nagy-Soper parton shower. An implementation of the algorithm within
the HELAC-DIPOLES Monte Carlo generator is used to address the uncertainties
and ambiguities of the matching scheme. First results obtained using the
Nagy-Soper parton shower implementation in DEDUCTOR in conjunction with the
HELAC-NLO framework are given for the pp -> top anti-top j + X process at the
LHC with sqrt(s)=8 TeV. Effects of resummation are discussed for various
observables.Comment: 53 pages, 18 figures, 3 tables. References and a few typos corrected,
acknowledgments added, dependence on the variation of the starting shower
time corrected, version to appear in JHE
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