Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Adaptive Training for Correlated Fading Channels with Feedback   We consider data transmission through a time-selective, correlated
(first-order Markov) Rayleigh fading channel subject to an average power
constraint. The channel is estimated at the receiver with a pilot signal, and
the estimate is fed back to the transmitter. The estimate is used for coherent
demodulation, and to adapt the data and pilot powers. We explicitly determine
the optimal pilot and data power control policies in a continuous-time limit
where the channel state evolves as an Ornstein-Uhlenbeck diffusion process, and
is estimated by a Kalman filter at the receiver. The optimal pilot policy
switches between zero and the maximum (peak-constrained) value (``bang-bang''
control), and approximates the optimal discrete-time policy at low
Signal-to-Noise Ratios (equivalently, large bandwidths). The switching boundary
is defined in terms of the system state (estimated channel mean and associated
error variance), and can be explicitly computed. Under the optimal policy, the
transmitter conserves power by decreasing the training power when the channel
is faded, thereby increasing the data rate. Numerical results show a
significant increase in achievable rate due to the adaptive training scheme
with feedback, relative to constant (non-adaptive) training, which does not
require feedback. The gain is more pronounced at relatively low SNRs and with
fast fading. Results are further verified through Monte Carlo simulations.

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The categories of this paper are: q-alg
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The categories of this paper are: atom-ph
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The categories of this paper are: q-bio
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The categories of this paper are: hep-ph
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The categories of this paper are: funct-an
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: dg-ga
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The categories of this paper are: supr-con
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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: econ
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The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph