Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Adaptive and Efficient Nonlinear Channel Equalization for Underwater
  Acoustic Communication   We investigate underwater acoustic (UWA) channel equalization and introduce
hierarchical and adaptive nonlinear channel equalization algorithms that are
highly efficient and provide significantly improved bit error rate (BER)
performance. Due to the high complexity of nonlinear equalizers and poor
performance of linear ones, to equalize highly difficult underwater acoustic
channels, we employ piecewise linear equalizers. However, in order to achieve
the performance of the best piecewise linear model, we use a tree structure to
hierarchically partition the space of the received signal. Furthermore, the
equalization algorithm should be completely adaptive, since due to the highly
non-stationary nature of the underwater medium, the optimal MSE equalizer as
well as the best piecewise linear equalizer changes in time. To this end, we
introduce an adaptive piecewise linear equalization algorithm that not only
adapts the linear equalizer at each region but also learns the complete
hierarchical structure with a computational complexity only polynomial in the
number of nodes of the tree. Furthermore, our algorithm is constructed to
directly minimize the final squared error without introducing any ad-hoc
parameters. We demonstrate the performance of our algorithms through highly
realistic experiments performed on accurately simulated underwater acoustic
channels.

11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
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The categories of this paper are: chao-dyn
19
The categories of this paper are: eess
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
15
The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
32
The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: plasm-ph