272 research outputs found
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Recursive least squares semi-blind beamforming for MIMO using decision directed adaptation and constant modulus criterion
A new semi-blind adaptive beamforming scheme is proposed for multi-input multi-output (MIMO) induced and space-
division multiple-access based wireless systems that employ high order phase shift keying signaling. A minimum number of training
symbols, very close to the number of receiver antenna elements, are used to provide a rough initial least squares estimate of the
beamformer0s weight vector. A novel cost function combining the constant modulus criterion with decision-directed adaptation is
adopted to adapt the beamformer weight vector. This cost function can be approximated as a quadratic form with a closed-form
solution, based on which we then derive the recursive least squares (RLS) semi-blind adaptive beamforming algorithm. This semi-blind
adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated
in our simulation study. Our proposed semi-blind RLS beamforming algorithm therefore provides an e±cient detection scheme for the
future generation of MIMO aided mobile communication systems
Coherent diffraction of single Rice Dwarf virus particles using hard X-rays at the Linac Coherent Light Source
Single particle diffractive imaging data from Rice Dwarf Virus (RDV) were recorded using the Coherent X-ray Imaging (CXI) instrument at the Linac Coherent Light Source (LCLS). RDV was chosen as it is a wellcharacterized model system, useful for proof-of-principle experiments, system optimization and algorithm development. RDV, an icosahedral virus of about 70 nm in diameter, was aerosolized and injected into the approximately 0.1 mu m diameter focused hard X-ray beam at the CXI instrument of LCLS. Diffraction patterns from RDV with signal to 5.9 angstrom ngstrom were recorded. The diffraction data are available through the Coherent X-ray Imaging Data Bank (CXIDB) as a resource for algorithm development, the contents of which are described here.11Ysciescopu
Superconductivity at 31 K in 111 type iron arsenide superconductor NaxFeAs induced by pressure
The effect of pressure on superconductivity of 111 type NaxFeAs is
investigated through temperature dependent electrical resistance measurement in
a diamond anvil cell. The superconducting transition temperature (Tc) increases
from 26 K to a maximum 31 K as the pressure increases from ambient to 3 GPa.
Further increasing pressure suppresses Tc drastically. The behavior of pressure
tuned Tc in NaxFeAs is much different from that in LixFeAs, although they have
the same Cu2Sb type structur
Performance analysis of distributed cluster-based MAC protocol for multiuser MIMO wireless networks
Energy efficiency of some non-cooperative, cooperative and hybrid communication schemes in multi-relay WSNs
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