25,199 research outputs found
Robust massive MIMO Equilization for mmWave systems with low resolution ADCs
Leveraging the available millimeter wave spectrum will be important for 5G.
In this work, we investigate the performance of digital beamforming with low
resolution ADCs based on link level simulations including channel estimation,
MIMO equalization and channel decoding. We consider the recently agreed 3GPP NR
type 1 OFDM reference signals. The comparison shows sequential DCD outperforms
MMSE-based MIMO equalization both in terms of detection performance and
complexity. We also show that the DCD based algorithm is more robust to channel
estimation errors. In contrast to the common believe we also show that the
complexity of MMSE equalization for a massive MIMO system is not dominated by
the matrix inversion but by the computation of the Gram matrix.Comment: submitted to WCNC 2018 Workshop
Density functional theory for hard-sphere mixtures: the White-Bear version Mark II
In the spirit of the White-Bear version of fundamental measure theory we
derive a new density functional for hard-sphere mixtures which is based on a
recent mixture extension of the Carnahan-Starling equation of state. In
addition to the capability to predict inhomogeneous density distributions very
accurately, like the original White-Bear version, the new functional improves
upon consistency with an exact scaled-particle theory relation in the case of
the pure fluid. We examine consistency in detail within the context of
morphological thermodynamics. Interestingly, for the pure fluid the degree of
consistency of the new version is not only higher than for the original
White-Bear version but also higher than for Rosenfeld's original fundamental
measure theory.Comment: 16 pages, 3 figures; minor changes; J. Phys.: Condens. Matter,
accepte
Ab initio many-body calculations of nucleon scattering on 4He, 7Li, 7Be, 12C and 16O
We combine a recently developed ab initio many-body approach capable of
describing simultaneously both bound and scattering states, the ab initio
NCSM/RGM, with an importance truncation scheme for the cluster eigenstate basis
and demostrate its applicability to nuclei with mass numbers as high as 17.
Using soft similarity renormalization group evolved chiral nucleon-nucleon
interactions, we first calculate nucleon-4He phase shifts, cross sections and
analyzing power. Next, we investigate nucleon scattering on 7Li, 7Be, 12C and
16O in coupled-channel NCSM/RGM calculations that include low-lying excited
states of these nuclei. We check the convergence of phase shifts with the basis
size and study A=8, 13, and 17 bound and unbound states. Our calculations
predict low-lying resonances in 8Li and 8B that have not been experimentally
clearly identified yet. We are able to reproduce reasonably well the structure
of the A=13 low lying states. However, we find that A=17 states cannot be
described without an improved treatment of 16O one-particle-one-hole
excitations and alpha clustering.Comment: 18 pages, 20 figure
Effective s- and p-Wave Contact Interactions in Trapped Degenerate Fermi Gases
The structure and stability of dilute degenerate Fermi gases trapped in an
external potential is discussed with special emphasis on the influence of s-
and p-wave interactions. In a first step an Effective Contact Interaction for
all partial waves is derived, which reproduces the energy spectrum of the full
potential within a mean-field model space. Using the s- and p-wave part the
energy density of the multi-component Fermi gas is calculated in Thomas-Fermi
approximation. On this basis the stability of the one- and two-component Fermi
gas against mean-field induced collapse is investigated. Explicit stability
conditions in terms of density and total particle number are given. For the
single-component system attractive p-wave interactions limit the density of the
gas. In the two-component case a subtle competition of s- and p-wave
interactions occurs and gives rise to a rich variety of phenomena. A repulsive
p-wave part, for example, can stabilize a two-component system that would
otherwise collapse due to an attractive s-wave interaction. It is concluded
that the p-wave interaction may have important influence on the structure of
degenerate Fermi gases and should not be discarded from the outset.Comment: 18 pages, 11 figures (using RevTEX4
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