Optimal Cooperative Power Allocation for Energy Harvesting Enabled Relay Networks

In this paper, we present a new power allocation scheme for a decode-and-forward (DF) relaying-enhanced cooperative wireless system. While both source and relay nodes may have limited traditional brown power supply or fixed green energy storage, the hybrid source node can also draw power from the surrounding radio frequency (RF) signals. In particular, we assume a deterministic RF energy harvesting (EH) model under which the signals transmitted by the relay serve as the renewable energy source for the source node. The amount of harvested energy is known for a given transmission power of the forwarding signal and channel condition between the source and relay nodes. To maximize the overall throughput while meeting the constraints imposed by the non-sustainable energy sources and the renewable energy source, an optimization problem is formulated and solved. Based on different harvesting efficiency and channel condition, closed form solutions are derived to obtain the optimal source and relay power allocation jointly. It is shown that instead of demanding high on-grid power supply or high green energy availability, the system can achieve compatible or higher throughput by utilizing the harvested energy

RF Energy Harvesting Enabled Power Sharing in Relay Networks

Through simultaneous energy and information transfer, radio frequency (RF) energy harvesting (EH) reduces the energy consumption of the wireless networks. It also provides a new approach for the wireless devices to share each other's energy storage, without relying on the power grid or traffic offloading. In this paper, we study RF energy harvesting enabled power balancing within the decode-and-forward (DF) relaying-enhanced cooperative wireless system. An optimal power allocation policy is proposed for the scenario where both source and relay nodes can draw power from the radio frequency signals transmitted by each other. To maximize the overall throughput while meeting the energy constraints imposed by the RF sources, an optimization problem is formulated and solved. Based on different harvesting efficiency and channel condition, closed form solutions for optimal joint source and relay power allocation are derived.Comment: An abbreviated version will be presented at IEEE online GreenComm, Nov., 201

Energy Harvesting Enabled Cooperative Networks Resource Allocation Techniques, Protocol Design And Performance Analysis

In In wireless cooperative communication networks, cooperative relaying techniques can be employed to mitigate fading and attenuation problems by positioning relay nodes between a transmitter and a receiver. Therefore, network performance such as efficiency, throughput, and reliability can be improved. However, energy-constrained wireless cooperative relay nodes have a limited viable lifetime,which cannot sustain steady network connectivity, thereby making reliable communication difficult. Recently, energy harvesting (EH) via radio frequency (RF)signals appears to be a solution for sustaining the lifetime of the wireless cooperative relay nodes. In the past years, researchers have proposed some resource allocation techniques and protocols for simultaneous wireless information and power transfer (SWIPT) in the wireless cooperative communication networks. Nevertheless, there are still a lot of challenges being faced by the researchers to achieve an efficient SWIPT in such network. In this work, a new energy saving (ES) resource allocation technique is proposed for RF-EH enabled cooperative networks by adopting time switching relaying (TSR) and power splitting relaying (PSR) protocols. This is based on the assumption that the relay node uses a certain proportion of the harvested power in the current transmission block and then save the remaining portion for the next transmission block. Unlike the previous works, in that the resource allocation techniques in RF-EH enabled cooperative networks have been considered under the assumption that the energy-constrained relay must utilize all of its harvested power in each transmission block. The proposed ES technique is then optimized by considering the optimization problems. Then, the scenario of EH-enabled cooperative network with the presence of an interfering transmitter is considered. A hybridized power-time splitting based relaying (HPTSR) protocol is also proposed with amplified-andforward (AF) and decode-and-forward (DF) relaying techniques by introducing a channel-based and power-time splitter into the relay receiver architecture are analyzed. Numerical results revealed that the proposed ES-TSR and ES-PSR protocols outperformed the existing TSR and PSR protocols with an energy efficiency gain of 13.87 % and 8.31 %, respectively, particularly, when the number of transmission block L 10. These results show that the proposed ES resource allocation technique is more energy efficient than the existing ones. At the optimal throughput value, the proposed AF HPTSR protocol outperformed the existing AF PSR, TSR, and time power switching relaying (TPSR) based protocols with a throughput gain of 54.18 %, 72.31 %, and 10.47 %, respectively. The proposed DF HPTSR protocol showed a performance gain of 2.81 % over the proposed AF HPTSR protocol. These results show that the proposed AF or DF HPTSR protocol can achieve a better throughput performance over the existing protocols, especially at high signal-to-noise ratio

Outage Analysis for SWIPT-Enabled Two-Way Cognitive Cooperative Communications

In this paper, we study a cooperative cognitive radio network (CCRN) where the secondary user-transmitter (SU-Tx) assists bi-directional communication between a pair of primary users (PUs) following the principle of two-way relaying. In return, it gets access to the spectrum of the PUs to enable its own transmission to SU-receiver (SU-Rx). Further, in order to support sustainable operation of the network, SU-Tx is assumed to harvest energy from the RF signals received from the PUs, using the technique of simultaneous wireless information and power transfer (SWIPT). Assuming a decode-and-forward behaviour and power-splitting based relaying protocol at SU-Tx, closed form expressions for outage probability of PU and SU are obtained. Simulation results validate our analytical results and illustrate spectrum-efficiency and energy-efficiency advantages of the proposed system over one-way relaying.Comment: 15 pages, 5 figures, Submitted to IEEE Transactions on Vehicular Technolog

Outage Analysis for SWIPT-Enabled Two-Way Cognitive Cooperative Communications

In this paper, we study a cooperative cognitive radio network (CCRN) where the secondary user-transmitter (SU-Tx) assists bi-directional communication between a pair of primary users (PUs) following the principle of two-way relaying. In return, it gets access to the spectrum of the PUs to enable its own transmission to SU-receiver (SU-Rx). Further, in order to support sustainable operation of the network, SU-Tx is assumed to harvest energy from the RF signals received from the PUs, using the technique of simultaneous wireless information and power transfer (SWIPT). Assuming a decode-and-forward behaviour and power-splitting based relaying protocol at SU-Tx, closed form expressions for outage probability of PU and SU are obtained. Simulation results validate our analytical results and illustrate spectrum-efficiency and energy-efficiency advantages of the proposed system over one-way relaying.Comment: 15 pages, 5 figures, Submitted to IEEE Transactions on Vehicular Technolog

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