19,446 research outputs found
Networked MIMO with Fractional Joint Transmission in Energy Harvesting Systems
This paper considers two base stations (BSs) powered by renewable energy
serving two users cooperatively. With different BS energy arrival rates, a
fractional joint transmission (JT) strategy is proposed, which divides each
transmission frame into two subframes. In the first subframe, one BS keeps
silent to store energy while the other transmits data, and then they perform
zero-forcing JT (ZF-JT) in the second subframe. We consider the average
sum-rate maximization problem by optimizing the energy allocation and the time
fraction of ZF-JT in two steps. Firstly, the sum-rate maximization for given
energy budget in each frame is analyzed. We prove that the optimal transmit
power can be derived in closed-form, and the optimal time fraction can be found
via bi-section search. Secondly, approximate dynamic programming (DP) algorithm
is introduced to determine the energy allocation among frames. We adopt a
linear approximation with the features associated with system states, and
determine the weights of features by simulation. We also operate the
approximation several times with random initial policy, named as policy
exploration, to broaden the policy search range. Numerical results show that
the proposed fractional JT greatly improves the performance. Also, appropriate
policy exploration is shown to perform close to the optimal.Comment: 33 pages, 7 figures, accepted by IEEE Transactions on Communication
Joint User Scheduling and Beam Selection Optimization for Beam-Based Massive MIMO Downlinks
In beam-based massive multiple-input multiple-output systems, signals are
processed spatially in the radio-frequency (RF) front-end and thereby the
number of RF chains can be reduced to save hardware cost, power consumptions
and pilot overhead. Most existing work focuses on how to select, or design
analog beams to achieve performance close to full digital systems. However,
since beams are strongly correlated (directed) to certain users, the selection
of beams and scheduling of users should be jointly considered. In this paper,
we formulate the joint user scheduling and beam selection problem based on the
Lyapunov-drift optimization framework and obtain the optimal scheduling policy
in a closed-form. For reduced overhead and computational cost, the proposed
scheduling schemes are based only upon statistical channel state information.
Towards this end, asymptotic expressions of the downlink broadcast channel
capacity are derived. To address the weighted sum rate maximization problem in
the Lyapunov optimization, an algorithm based on block coordinated update is
proposed and proved to converge to the optimum of the relaxed problem. To
further reduce the complexity, an incremental greedy scheduling algorithm is
also proposed, whose performance is proved to be bounded within a constant
multiplicative factor. Simulation results based on widely-used spatial channel
models are given. It is shown that the proposed schemes are close to optimal,
and outperform several state-of-the-art schemes.Comment: Submitted to Trans. Wireless Commu
Efficient -particle state concentration with different parity check gates
We present an universal way to concentrate an arbitrary -particle
less-entangled state into a maximally entangled state with different
parity check gates. It comprises two protocols. The first protocol is based on
the linear optical elements say the partial parity check gate and the second
one uses the quantum nondemolition (QND) to construct the complete parity check
gate. Both of which can achieve the concentration task. These protocols have
several advantages. First, it can obtain a maximally entangled W state only
with the help of some single photons, which greatly reduces the number of
entanglement resources. Second, in the first protocol, only linear optical
elements are required which is feasible with current techniques. Third, in the
second protocol, it can be repeated to perform the concentration step and get a
higher success probability. All these advantages make it be useful in current
quantum communication and computation applications.Comment: 11pages,8figure
Dynamic Compression Ratio Selection for Edge Inference Systems with Hard Deadlines
Implementing machine learning algorithms on Internet of things (IoT) devices
has become essential for emerging applications, such as autonomous driving,
environment monitoring. But the limitations of computation capability and
energy consumption make it difficult to run complex machine learning algorithms
on IoT devices, especially when latency deadline exists. One solution is to
offload the computation intensive tasks to the edge server. However, the
wireless uploading of the raw data is time consuming and may lead to deadline
violation. To reduce the communication cost, lossy data compression can be
exploited for inference tasks, but may bring more erroneous inference results.
In this paper, we propose a dynamic compression ratio selection scheme for edge
inference system with hard deadlines. The key idea is to balance the tradeoff
between communication cost and inference accuracy. By dynamically selecting the
optimal compression ratio with the remaining deadline budgets for queued tasks,
more tasks can be timely completed with correct inference under limited
communication resources. Furthermore, information augmentation that retransmits
less compressed data of task with erroneous inference, is proposed to enhance
the accuracy performance. While it is often hard to know the correctness of
inference, we use uncertainty to estimate the confidence of the inference, and
based on that, jointly optimize the information augmentation and compression
ratio selection. Lastly, considering the wireless transmission errors, we
further design a retransmission scheme to reduce performance degradation due to
packet losses. Simulation results show the performance of the proposed schemes
under different deadlines and task arrival rates.Comment: 11 pages, 14 figure
Efficient entanglement concentration for three-photon W states with parity check measurement
We present an optimal entanglement concentration ECP for an arbitrary
less-entangled W state. By two of the parties say Alice and Charlie performing
one parity check measurements, they can obtain the maximally entangled W state
with a certain probability. Otherwise, they can obtain another lesser-entangled
W state with another probability, which can be used to reconcentrated into a
maximally entangled W state. By iterating this ECP several times, it has the
maximal success probability. This ECP maybe an optimal one and is useful in
current quantum information processing.Comment: 10 pages, 8 figure
Efficient entanglement concentration for arbitrary less-entangled NOON state assisted with single photon
We put forward two efficient entanglement concentration protocols (ECPs) for
distilling the maximally entangled NOON state from arbitrary less-entangled
NOON state with only an auxiliary single photon. With the help of the weak
cross-Kerr nonlinearities, both the two ECPs can be used repeatedly to get a
high success probability. In the first ECP, the auxiliary single photon should
be shared by the two parties say Alice and Bob. In the second ECP, the
auxiliary single photon is only possessed by Bob, which can greatly increase
the practical success probability by avoiding the transmission loss. Moreover,
Bob can operate the whole protocol alone, which makes the protocol more simple.
Therefore, our two ECPs, especially the second ECP may be more useful and
convenient in the current quantum information processing.Comment: 10 pages, 3 figure
Efficient entanglement purification for polarization logic Bell state with the photonic Faraday rotation
Logic-qubit entanglement is a promising resource in quantum information
processing, especially in future large-scale quantum networks. In the paper, we
put forward an efficient entanglement purification protocol (EPP) for nonlocal
mixed logic entangled states with the bit-flip error in the logic qubits of the
logic Bell state, resorting to the photon-atom interaction in low-quality (Q)
cavity and atomic state measurement. Different from existing EPPs, this
protocol can also purify the logic phase-flip error, and the bit-flip error and
the phase-flip error in physic qubit. During the protocol, we only require to
measure the atom states, and it is useful for improving the entanglement of
photon systems in future large-scale quantum networks.Comment: 14 page, 6 figure
Distilling and protecting the single-photon entangled state
We propose two efficient entanglement concentration protocols (ECPs) for
arbitrary less-entangled single-photon entanglement (SPE). Different from all
the previous ECPs, these protocols not only can obtain the maximally SPE, but
also can protect the single qubit information encoded in the polarization
degree of freedom. These protocols only require one pair of less-entangled
single-photon entangled state and some auxiliary single photons, which makes
them economical. The first ECP is operated with the linear optical elements,
which can be realized in current experiment. The second ECP adopts the
cross-Kerr nonlinearities. Moreover, the second ECP can be repeated to
concentrate the discard states in some conventional ECPs, so that it can get a
high success probability. Based on above properties, our ECPs may be useful in
current and future quantum communication.Comment: 11 pages, 4 figure
On -Convergence of Fourier Series Under Condition
Let be a real-valued even function with its Fourier series and let be the -th partial sum of the Fourier series. It is well-known that if
the nonnegative sequence is decreasing and , then We weaken the
monotone condition in this classical result to the so-called mean value bounded
variation () condition. The generalization of the above classical result
in real-valued function space is presented as a special case of the main result
in this paper which gives the % -convergence of a function in complex space. We also give results on -approximation of a
function under the condition.Comment: 13 Pages, Accepted by Canad. Math. Bul
Ultimate Generalization to Monotonicity for Uniform Convergence of Trigonometric Series
Chaundy and Jolliffe [4] proved that if is a non-increasing
(monotonic) real sequence with , then a
necessary and sufficient condition for the uniform convergence of the series
is . We
generalize (or weaken) the monotonic condition on the coefficient sequence
in this classical result to the so-called mean value bounded
variation condition and prove that the generalized condition cannot be weakened
further. We also establish an analogue to the generalized Chaundy and Jolliffe
theorem in the complex space.Comment: 21 page
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