954 research outputs found
Power Control and Beamforming Design for SWIPT in AF Two-Way Relay Networks
In this paper, we study the problem of joint power control and beamforming design for simultaneous wireless information and power transfer (SWIPT) in an amplify-and-forward (AF) based two-way relaying (TWR) network. The considered system model consists of two source nodes and a relay node. Two single-antenna source nodes receive information and energy simultaneously via power splitting (PS) from the signals sent by a multi-antenna relay node. Our objective is to maximize the weighted sum power at the two source nodes subject to quality of service (QoS) constraints and the transmit power constraints. However, the joint optimization of the relay beamforming matrix, the source transmit power and PS ratio is intractable. To find a closed-form solution of the formulated problem, we decouple the primal problem into two subproblems. In the first problem, we intend to optimize the beamforming vectors for given transmit powers and PS ratio. In the second subproblem, we optimize the remaining parameters with obtained beamformers. It is worth noting that although the corresponding subproblem are nonconvex, the optimal solution of each subproblem can be found by using certain techniques. The iterative optimization algorithm finally converges. Simulation results verify the effectiveness of the proposed joint design
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
Joint Power Splitting and Secure Beamforming Design in the Wireless-powered Untrusted Relay Networks
In this work, we maximize the secrecy rate of the wireless-powered untrusted
relay network by jointly designing power splitting (PS) ratio and relay
beamforming with the proposed global optimal algorithm (GOA) and local optimal
algorithm (LOA). Different from the literature, artificial noise (AN) sent by
the destination not only degrades the channel condition of the eavesdropper to
improve the secrecy rate, but also becomes a new source of energy powering the
untrusted relay based on PS. Hence, it is of high economic benefits and
efficiency to take advantage of AN compared with the literature. Simulation
results show that LOA can achieve satisfactory secrecy rate performance
compared with that of GOA, but with less computation time.Comment: Submitted to GlobeCom201
Resource Allocation in Wireless Networks with RF Energy Harvesting and Transfer
Radio frequency (RF) energy harvesting and transfer techniques have recently
become alternative methods to power the next generation of wireless networks.
As this emerging technology enables proactive replenishment of wireless
devices, it is advantageous in supporting applications with quality-of-service
(QoS) requirement. This article focuses on the resource allocation issues in
wireless networks with RF energy harvesting capability, referred to as RF
energy harvesting networks (RF-EHNs). First, we present an overview of the
RF-EHNs, followed by a review of a variety of issues regarding resource
allocation. Then, we present a case study of designing in the receiver
operation policy, which is of paramount importance in the RF-EHNs. We focus on
QoS support and service differentiation, which have not been addressed by
previous literatures. Furthermore, we outline some open research directions.Comment: To appear in IEEE Networ
Multi-Pair Two-Way Relay Network with Harvest-Then-Transmit Users: Resolving Pairwise Uplink-Downlink Coupling
While two-way relaying is a promising way to enhance the spectral efficiency
of wireless networks, the imbalance of relay-user distances may lead to
excessive wireless power at the nearby-users. To exploit the excessive power,
the recently proposed harvest-then-transmit technique can be applied. However,
it is well-known that harvest-then-transmit introduces uplink-downlink coupling
for a user. Together with the co-dependent relationship between paired users
and interference among multiple user pairs, wirelessly powered two-way relay
network suffers from the unique pairwise uplink-downlink coupling, and the
joint uplink-downlink network design is nontrivial. To this end, for the one
pair users case, we show that a global optimal solution can be obtained. For
the general case of multi-pair users, based on the rank-constrained difference
of convex program, a convergence guaranteed iterative algorithm with an
efficient initialization is proposed. Furthermore, a lower bound to the
performance of the optimal solution is derived by introducing virtual receivers
at relay. Numerical results on total transmit power show that the proposed
algorithm achieves a transmit power value close to the lower bound
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