879 research outputs found
Multi-user Scheduling Schemes for Simultaneous Wireless Information and Power Transfer
In this paper, we study the downlink multi-user scheduling problem for a
time-slotted system with simultaneous wireless information and power transfer.
In particular, in each time slot, a single user is scheduled to receive
information, while the remaining users opportunistically harvest the ambient
radio frequency (RF) energy. We devise novel scheduling schemes in which the
tradeoff between the users' ergodic capacities and their average amount of
harvested energy can be controlled. To this end, we modify two fair scheduling
schemes used in information-only transfer systems. First, proportionally fair
maximum normalized signal-to-noise ratio (N-SNR) scheduling is modified by
scheduling the user having the jth ascendingly ordered (rather than the
maximum) N-SNR. We refer to this scheme as order-based N-SNR scheduling.
Second, conventional equal-throughput (ET) fair scheduling is modified by
scheduling the user having the minimum moving average throughput among the set
of users whose N-SNR orders fall into a certain set of allowed orders Sa
(rather than the set of all users). We refer to this scheme as order-based ET
scheduling. The feasibility conditions required for the users to achieve ET
with this scheme are also derived. We show that the smaller the selection order
j for the order-based N-SNR scheme, and the lower the orders in Sa for the
order-based ET scheme, the higher the average amount of energy harvested by the
users at the expense of a reduction in their ergodic capacities. We analyze the
performance of the considered scheduling schemes for independent and
non-identically distributed (i.n.d.) Ricean fading channels, and provide
closed-form results for the special case of i.n.d. Rayleigh fading.Comment: 6 pages, 3 figures. Submitted for possible conference publicatio
Optimized Training Design for Wireless Energy Transfer
Radio-frequency (RF) enabled wireless energy transfer (WET), as a promising
solution to provide cost-effective and reliable power supplies for
energy-constrained wireless networks, has drawn growing interests recently. To
overcome the significant propagation loss over distance, employing
multi-antennas at the energy transmitter (ET) to more efficiently direct
wireless energy to desired energy receivers (ERs), termed \emph{energy
beamforming}, is an essential technique for enabling WET. However, the
achievable gain of energy beamforming crucially depends on the available
channel state information (CSI) at the ET, which needs to be acquired
practically. In this paper, we study the design of an efficient channel
acquisition method for a point-to-point multiple-input multiple-output (MIMO)
WET system by exploiting the channel reciprocity, i.e., the ET estimates the
CSI via dedicated reverse-link training from the ER. Considering the limited
energy availability at the ER, the training strategy should be carefully
designed so that the channel can be estimated with sufficient accuracy, and yet
without consuming excessive energy at the ER. To this end, we propose to
maximize the \emph{net} harvested energy at the ER, which is the average
harvested energy offset by that used for channel training. An optimization
problem is formulated for the training design over MIMO Rician fading channels,
including the subset of ER antennas to be trained, as well as the training time
and power allocated. Closed-form solutions are obtained for some special
scenarios, based on which useful insights are drawn on when training should be
employed to improve the net transferred energy in MIMO WET systems.Comment: 30 pages, 9 figures, to appear in IEEE Trans. on Communication
Optimal Multiuser Scheduling Schemes for Simultaneous Wireless Information and Power Transfer
In this paper, we study the downlink multiuser scheduling problem for systems
with simultaneous wireless information and power transfer (SWIPT). We design
optimal scheduling algorithms that maximize the long-term average system
throughput under different fairness requirements, such as proportional fairness
and equal throughput fairness. In particular, the algorithm designs are
formulated as non-convex optimization problems which take into account the
minimum required average sum harvested energy in the system. The problems are
solved by using convex optimization techniques and the proposed optimization
framework reveals the tradeoff between the long-term average system throughput
and the sum harvested energy in multiuser systems with fairness constraints.
Simulation results demonstrate that substantial performance gains can be
achieved by the proposed optimization framework compared to existing suboptimal
scheduling algorithms from the literature.Comment: Accepted for presentation at the European Signal Processing
Conference 201
SWIPT with practical modulation and RF energy harvesting sensitivity
In this paper, we investigate the performance of
simultaneous wireless information and power transfer (SWIPT)
in a point-to-point system, adopting practical M-ary modulation.
We take into account the fact that the receiver’s radio-frequency
(RF) energy harvesting circuit can only harvest energy when
the received signal power is greater than a certain sensitivity
level. For both power-splitting (PS) and time-switching (TS)
schemes, we derive the energy harvesting performance as well
as the information decoding performance for the Nakagamim
fading channel. We also analyze the performance tradeoff
between energy harvesting and information decoding by studying
an optimization problem, which maximizes the information
decoding performance and satisfies a constraint on the minimum
harvested energy. Our analysis shows that (i) for the PS scheme,
modulations with high peak-to-average power ratio achieve better
energy harvesting performance, (ii) for the TS scheme, it is
desirable to concentrate the power for wireless power transfer
in order to minimize the non-harvested energy caused by the
RF energy harvesting sensitivity level, and (iii) channel fading is
beneficial for energy harvesting in both PS and TS schemes.ARC Discovery Projects Grant DP14010113
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