2,648 research outputs found
Performance Analysis and Resource Allocation of STAR-RIS Aided Wireless-Powered NOMA System
This paper proposes a simultaneous transmitting and reflecting reconfigurable
intelligent surface (STAR-RIS) aided wireless-powered non-orthogonal multiple
access (NOMA) system, which includes an access point (AP), a STAR-RIS, and two
non-orthogonal users located at both sides of the STAR-RIS. In this system, the
users first harvest the radio-frequency energy from the AP in the downlink,
then adopt the harvested energy to transmit information to the AP in the uplink
concurrently. Two policies are considered for the proposed system. The first
one assumes that the time-switching protocol is used in the downlink while the
energy-splitting protocol is adopted in the uplink, named TEP. The second one
assumes that the energy-splitting protocol is utilized in both the downlink and
uplink, named EEP. The outage probability, sum throughput, and average age of
information (AoI) of the proposed system with TEP and EEP are investigated over
Nakagami-m fading channels. In addition, we also analyze the outage
probability, sum throughput, and average AoI of the STAR-RIS aided
wireless-powered time-division-multiple-access (TDMA) system. Simulation and
numerical results show that the proposed system with TEP and EEP outperforms
baseline schemes, and significantly improves sum throughput performance but
reduces outage probability and average AoI performance compared to the STAR-RIS
aided wireless-powered TDMA system. Furthermore, to maximize the sum throughput
and ensure a certain average AoI, we design a genetic-algorithm based time
allocation and power allocation (GA-TAPA) algorithm. Simulation results
demonstrate that the proposed GA-TAPA method can significantly improve the sum
throughput by adaptively adjusting system parameters.Comment: 30 pages, 12 figure
Resource Allocation for Wireless-Powered Full-Duplex Relaying Systems with Nonlinear Energy Harvesting Efficiency
In wireless power transfer (WPT)-assisted relaying systems, spectral efficiency (SE) of source-relay link plays a dominant role in system SE performance due to the limited transmission power at the WPT-aided relay. In this paper, we propose a novel protocol for a downlink orthogonal frequency division multiple access (OFDMA) system with a WPT-aided relay operating in full-duplex (FD) decode-and-forward (DF) mode, where the time slot durations of the source-relay and relay-users hops are designed to be dynamic, to enhance the utilization of degrees of freedom and hence the system SE. In particular, a multiple-input and signal-output (MISO) source-relay channel is considered to satisfy the stringent sensitivity of the energy harvesting (EH) circuit at the relay, while a single-input and single-output (SISO) relay-user channel is considered to alleviate the power consumption at the relay node. Taking into account the non-linearity of EH efficiency, a near-optimal iteration-based dynamic WPT-aided FD relaying (A-FR) algorithm is developed by jointly optimizing the time slot durations, subcarriers, and transmission power at the source and the relay. Furthermore, self-interference generated at the relay is utilized as a vital energy source rather than being canceled, which increases substantially the total energy harvested at the FD relay. We also reveal some implicit characteristics of the considered WPT-aided FD relaying system through intensive discussions. Simulation results confirm that the proposed A-FR achieves a significant enhancement in terms of SE with different relay's locations and the number of users, compared to the conventional symmetric WPT-aided FD relaying (S-FR) and the time-switching-based WPT-aided FD relaying (TS-FR) benchmarks
An Energy-Efficient Controller for Wirelessly-Powered Communication Networks
In a wirelessly-powered communication network (WPCN), an energy access point
(E-AP) supplies the energy needs of the network nodes through radio frequency
wave transmission, and the nodes store their received energy in their batteries
for possible data transmission. In this paper, we propose an online control
policy for energy transfer from the E-AP to the wireless nodes and for data
transfer among the nodes. With our proposed control policy, all data queues of
the nodes are stable, while the average energy consumption of the network is
shown to be within a bounded gap of the minimum energy required for stabilizing
the network. Our proposed policy is designed using a quadratic Lyapunov
function to capture the limitations on the energy consumption of the nodes
imposed by their battery levels. We show that under the proposed control
policy, the backlog level in the data queues and the stored energy level in the
batteries fluctuate in small intervals around some constant levels.
Consequently, by imposing negligible average data drop rate, the data buffer
size and the battery capacity of the nodes can be significantly reduced
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