1,269 research outputs found
Energy-Efficient Power Allocation in OFDM Systems with Wireless Information and Power Transfer
This paper considers an orthogonal frequency division multiplexing (OFDM)
downlink point-to-point system with simultaneous wireless information and power
transfer. It is assumed that the receiver is able to harvest energy from noise,
interference, and the desired signals.
We study the design of power allocation algorithms maximizing the energy
efficiency of data transmission (bit/Joule delivered to the receiver). In
particular, the algorithm design is formulated as a high-dimensional non-convex
optimization problem which takes into account the circuit power consumption,
the minimum required data rate, and a constraint on the minimum power delivered
to the receiver. Subsequently, by exploiting the properties of nonlinear
fractional programming, the considered non-convex optimization problem, whose
objective function is in fractional form, is transformed into an equivalent
optimization problem having an objective function in subtractive form, which
enables the derivation of an efficient iterative power allocation algorithm. In
each iteration, the optimal power allocation solution is derived based on dual
decomposition and a one-dimensional search. Simulation results illustrate that
the proposed iterative power allocation algorithm converges to the optimal
solution, and unveil the trade-off between energy efficiency, system capacity,
and wireless power transfer: (1) In the low transmit power regime, maximizing
the system capacity may maximize the energy efficiency. (2) Wireless power
transfer can enhance the energy efficiency, especially in the interference
limited regime.Comment: 6 pages, Accepted for presentation at the IEEE International
Conference on Communications (ICC) 201
Energy-Efficient Resource Allocation in Multiuser OFDM Systems with Wireless Information and Power Transfer
In this paper, we study the resource allocation algorithm design for
multiuser orthogonal frequency division multiplexing (OFDM) downlink systems
with simultaneous wireless information and power transfer. The algorithm design
is formulated as a non-convex optimization problem for maximizing the energy
efficiency of data transmission (bit/Joule delivered to the users). In
particular, the problem formulation takes into account the minimum required
system data rate, heterogeneous minimum required power transfers to the users,
and the circuit power consumption. Subsequently, by exploiting the method of
time-sharing and the properties of nonlinear fractional programming, the
considered non-convex optimization problem is solved using an efficient
iterative resource allocation algorithm. For each iteration, the optimal power
allocation and user selection solution are derived based on Lagrange dual
decomposition. Simulation results illustrate that the proposed iterative
resource allocation algorithm achieves the maximum energy efficiency of the
system and reveal how energy efficiency, system capacity, and wireless power
transfer benefit from the presence of multiple users in the system.Comment: 6 pages. The paper has been accepted for publication at the IEEE
Wireless Communications and Networking Conference (WCNC) 2013, Shanghai,
China, Apr. 201
Robust Transmissions in Wireless Powered Multi-Relay Networks with Chance Interference Constraints
In this paper, we consider a wireless powered multi-relay network in which a
multi-antenna hybrid access point underlaying a cellular system transmits
information to distant receivers. Multiple relays capable of energy harvesting
are deployed in the network to assist the information transmission. The hybrid
access point can wirelessly supply energy to the relays, achieving multi-user
gains from signal and energy cooperation. We propose a joint optimization for
signal beamforming of the hybrid access point as well as wireless energy
harvesting and collaborative beamforming strategies of the relays. The
objective is to maximize network throughput subject to probabilistic
interference constraints at the cellular user equipment. We formulate the
throughput maximization with both the time-switching and power-splitting
schemes, which impose very different couplings between the operating parameters
for wireless power and information transfer. Although the optimization problems
are inherently non-convex, they share similar structural properties that can be
leveraged for efficient algorithm design. In particular, by exploiting
monotonicity in the throughput, we maximize it iteratively via customized
polyblock approximation with reduced complexity. The numerical results show
that the proposed algorithms can achieve close to optimal performance in terms
of the energy efficiency and throughput.Comment: 14 pages, 8 figure
On the Capacity of SWIPT Systems with a Nonlinear Energy Harvesting Circuit
In this paper, we study information-theoretic limits for simultaneous
wireless information and power transfer (SWIPT) systems employing a practical
nonlinear radio frequency (RF) energy harvesting (EH) receiver. In particular,
we consider a three-node system with one transmitter that broadcasts a common
signal to separated information decoding (ID) and EH receivers. Owing to the
nonlinearity of the EH receiver circuit, the efficiency of wireless power
transfer depends significantly on the waveform of the transmitted signal. In
this paper, we aim to answer the following fundamental question: What is the
optimal input distribution of the transmit waveform that maximizes the rate of
the ID receiver for a given required harvested power at the EH receiver? In
particular, we study the capacity of a SWIPT system impaired by additive white
Gaussian noise (AWGN) under average-power (AP) and peak-power (PP) constraints
at the transmitter and an EH constraint at the EH receiver. Using Hermite
polynomial bases, we prove that the optimal capacity-achieving input
distribution that maximizes the rate-energy region is unique and discrete with
a finite number of mass points. Furthermore, we show that the optimal input
distribution for the same problem without PP constraint is discrete whenever
the EH constraint is active and continuous zero-mean Gaussian, otherwise. Our
numerical results show that the rate-energy region is enlarged for a larger PP
constraint and that the rate loss of the considered SWIPT system compared to
the AWGN channel without EH receiver is reduced by increasing the AP budget.Comment: 7 pages, 4 figures, submitted for possible conference publicatio
Jointly Optimal Spatial Channel Assignment and Power Allocation for MIMO SWIPT Systems
The joint design of spatial channel assignment and power allocation in
Multiple Input Multiple Output (MIMO) systems capable of Simultaneous Wireless
Information and Power Transfer (SWIPT) is studied. Assuming availability of
channel state information at both communications ends, we maximize the
harvested energy at the multi-antenna receiver, while satisfying a minimum
information rate requirement for the MIMO link. We first derive the globally
optimal eigenchannel assignment and power allocation design, and then present a
practically motivated tight closed-form approximation for the optimal design
parameters. Selected numerical results verify the validity of the optimal
solution and provide useful insights on the proposed designs as well as the
pareto-optimal rate-energy tradeoff.Comment: 5 pages; 4 figures; accepted to IEEE journal 201
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