11,240 research outputs found
On the Matrix Inversion Approximation Based on Neumann Series in Massive MIMO Systems
Zero-Forcing (ZF) has been considered as one of the potential practical
precoding and detection method for massive MIMO systems. One of the most
important advantages of massive MIMO is the capability of supporting a large
number of users in the same time-frequency resource, which requires much larger
dimensions of matrix inversion for ZF than conventional multi-user MIMO
systems. In this case, Neumann Series (NS) has been considered for the Matrix
Inversion Approximation (MIA), because of its suitability for massive MIMO
systems and its advantages in hardware implementation. The
performance-complexity trade-off and the hardware implementation of NS-based
MIA in massive MIMO systems have been discussed. In this paper, we analyze the
effects of the ratio of the number of massive MIMO antennas to the number of
users on the performance of NS-based MIA. In addition, we derive the
approximation error estimation formulas for different practical numbers of
terms of NS-based MIA. These results could offer useful guidelines for
practical massive MIMO systems.Comment: accepted to conference; Proc. IEEE ICC 201
Efficient estimation of moments in linear mixed models
In the linear random effects model, when distributional assumptions such as
normality of the error variables cannot be justified, moments may serve as
alternatives to describe relevant distributions in neighborhoods of their
means. Generally, estimators may be obtained as solutions of estimating
equations. It turns out that there may be several equations, each of them
leading to consistent estimators, in which case finding the efficient estimator
becomes a crucial problem. In this paper, we systematically study estimation of
moments of the errors and random effects in linear mixed models.Comment: Published in at http://dx.doi.org/10.3150/10-BEJ330 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
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