17,116 research outputs found
Phase Estimation and Phase Ambiguity Resolution by Message Passing
Several code-aided algorithms for phase estimation have recently been proposed. While some of them are ad-hoc, others are derived in a systematic way. The latter can be divided into two different classes: phase estimators derived from the expectation-maximization (EM) principle and estimators that are approximations of the sum-product message passing algorithm. In this paper, the main differences and similarities between these two classes of phase estimation algorithms are outlined and their performance and complexity is compared. Furthermore, an alternative criterion for phase ambiguity resolution is presented and compared to an EM based approach proposed earlier
Blind Signal Detection in Massive MIMO: Exploiting the Channel Sparsity
In practical massive MIMO systems, a substantial portion of system resources
are consumed to acquire channel state information (CSI), leading to a
drastically lower system capacity compared with the ideal case where perfect
CSI is available. In this paper, we show that the overhead for CSI acquisition
can be largely compensated by the potential gain due to the sparsity of the
massive MIMO channel in a certain transformed domain. To this end, we propose a
novel blind detection scheme that simultaneously estimates the channel and data
by factorizing the received signal matrix. We show that by exploiting the
channel sparsity, our proposed scheme can achieve a DoF very close to the ideal
case, provided that the channel is sufficiently sparse. Specifically, the
achievable degree of freedom (DoF) has a fractional gap of only from the
ideal DoF, where is the channel coherence time. This is a remarkable
advance for understanding the performance limit of the massive MIMO system. We
further show that the performance advantage of our proposed scheme in the
asymptotic SNR regime carries over to the practical SNR regime. Numerical
results demonstrate that our proposed scheme significantly outperforms its
counterpart schemes in the practical SNR regime under various system
configurations.Comment: 32 pages, 9 figures, submitted to IEEE Trans. Commu
Systematic effects from black hole-neutron star waveform model uncertainties on the neutron star equation of state
We identify various contributors of systematic effects in the measurement of
the neutron star (NS) tidal deformability and quantify their magnitude for
several types of neutron star - black hole (NSBH) binaries. Gravitational waves
from NSBH mergers contain information about the components' masses and spins as
well as the NS equation of state. Extracting this information requires
comparison of the signal in noisy detector data with theoretical templates
derived from some combination of post-Newtonian (PN) approximants, effective
one-body (EOB) models and %analytic fits to numerical relativity (NR)
simulations. The accuracy of these templates is limited by errors in the NR
simulations, by the approximate nature of the PN/EOB waveforms, and by the
hybridization procedure used to combine them. In this paper, we estimate the
impact of these errors by constructing and comparing a set of PN-NR hybrid
waveforms, for the first time with NR waveforms from two different codes,
namely, SpEC and SACRA, for such systems. We then attempt to recover the
parameters of the binary using two non-precessing template approximants. We
find that systematic errors are too large for tidal effects to be accurately
characterized for any realistic NS equation of state model. We conclude that
NSBH waveform models must be significantly improved if they are to be useful
for the extraction of NS equation of state information or even for
distinguishing NSBH systems from binary black holes
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