514 research outputs found
Beamforming Optimization for Full-Duplex Wireless-powered MIMO Systems
We propose techniques for optimizing transmit beamforming in a full-duplex
multiple-input-multiple-output (MIMO) wireless-powered communication system,
which consists of two phases. In the first phase, the wireless-powered mobile
station (MS) harvests energy using signals from the base station (BS), whereas
in the second phase, both MS and BS communicate to each other in a full-duplex
mode. When complete instantaneous channel state information (CSI) is available,
the BS beamformer and the time-splitting (TS) parameter of energy harvesting
are jointly optimized in order to obtain the BS-MS rate region. The joint
optimization problem is non-convex, however, a computationally efficient
optimum technique, based upon semidefinite relaxation and line-search, is
proposed to solve the problem. A sub-optimum zero-forcing approach is also
proposed, in which a closed-form solution of TS parameter is obtained. When
only second-order statistics of transmit CSI is available, we propose to
maximize the ergodic information rate at the MS, while maintaining the outage
probability at the BS below a certain threshold. An upper bound for the outage
probability is also derived and an approximate convex optimization framework is
proposed for efficiently solving the underlying non-convex problem. Simulations
demonstrate the advantages of the proposed methods over the sub-optimum and
half-duplex ones.Comment: 14 pages, accepte
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
Multisource power splitting energy harvesting relaying network in half-duplex system over block Rayleigh fading channel: System performance analysis
Energy harvesting and information transferring simultaneously by radio frequency (RF) is considered as the novel solution for green-energy wireless communications. From that point of view, the system performance (SP) analysis of multisource power splitting (PS) energy harvesting (EH) relaying network (RN) over block Rayleigh-fading channels is presented and investigated. We investigate the system in both delay-tolerant transmission (DTT), and delay-limited transmission (DLT) modes and devices work in the half-duplex (HD) system. In this model system, the closed-form (CF) expressions for the outage probability (OP), system throughput (ST) in DLT mode and for ergodic capacity (EC) for DTT mode are analyzed and derived, respectively. Furthermore, CF expression for the symbol errors ratio (SER) is demonstrated. Then, the optimal PS factor is investigated. Finally, a Monte Carlo simulation is used for validating the analytical expressions concerning with all system parameters (SP).Web of Science81art. no. 6
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