Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Low-Complexity Channel Estimation in Large-Scale MIMO using Polynomial
  Expansion   This paper considers pilot-based channel estimation in large-scale
multiple-input multiple-output (MIMO) communication systems, also known as
"massive MIMO". Unlike previous works on this topic, which mainly considered
the impact of inter-cell disturbance due to pilot reuse (so-called pilot
contamination), we are concerned with the computational complexity. The
conventional minimum mean square error (MMSE) and minimum variance unbiased
(MVU) channel estimators rely on inverting covariance matrices, which has cubic
complexity in the multiplication of number of antennas at each side. Since this
is extremely expensive when there are hundreds of antennas, we propose to
approximate the inversion by an L-order matrix polynomial. A set of
low-complexity Bayesian channel estimators, coined Polynomial ExpAnsion CHannel
(PEACH) estimators, are introduced. The coefficients of the polynomials are
optimized to yield small mean square error (MSE). We show numerically that
near-optimal performance is achieved with low polynomial orders. In practice,
the order L can be selected to balance between complexity and MSE.
Interestingly, pilot contamination is beneficial to the PEACH estimators in the
sense that smaller L can be used to achieve near-optimal MSEs.

28
The categories of this paper are: alg-geom
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
13
The categories of this paper are: quant-ph
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
33
The categories of this paper are: plasm-ph
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
16
The categories of this paper are: stat
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The categories of this paper are: eess
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The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
12
The categories of this paper are: nucl-th