Article

Unification of RF Energy Harvesting Schemes under Mixed Rayleigh-Rician Fading Channels

Authors:
  • The University of Oklahoma Tulsa OK USA
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Abstract

In this work, a generalized approach is proposed to review the performance of relaying designs with energy harvesting capability. The unified modeling of generalized energy harvesting relaying (GEHR) design covers the non-energy harvesting designs and the well-known energy harvesting designs, i.e., time-based relaying (TR) and power-based relaying (PR). Moreover, the hybrid of both TR and PR designs is also catered. We find the mathematical representations for the outage probability, ergodic capacity and average throughput in Rayleigh fading channels for amplify-and-forward (AF) and decode-and-forward (DF) relaying modes. The closed-form expressions are derived for the outage probability. To validate that GEHR design is a generalization of TR and PR designs, we study the individual cases of GEHR design from the perspectives of schematic diagram, signal analysis and the performance evaluation parameters comparison. Furthermore, the GEHR design is studied for the mixed Rayleigh-Rician fading channels. We considered two sub-cases of mixed fading, i.e., in case 01, source to relay (SR) link is considered as Rayleigh channel and relay to destination (RD) link is considered as a Rician channel. Conversely, in case 02, SR link is taken as Rician channel and RD link is a Rayleigh channel. We find the mathematical expressions for the ergodic capacity, outage probability and average throughput for DF and AF relaying for both cases of mixed fading channels. The analytical results in both channel configurations are presented for throughput and verified using extensive Monte-Carlo simulations. The results show that the proposed GEHR design can be set to work as not only for the conventional TR and PR designs but also for hybrid of them. Furthermore, with some slight modifications in the proposed design, it can work as a conventional non-energy harvesting cooperative relaying model.

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... The outage probability of AF and DF networks employing HP, having non-linear EH behaviour is studied in [20] and [21], whereas having multiple relays is discussed in [22] and [23]. On the contrary, the outage of HP in AF and DF networks over asymmetric fading channels is investigated in [24] and [25], respectively. A Time Switching Protocol with Adaptive Power Splitting (TS-APS) for multi-relay DF network is discussed in [26]. ...
... It can be simplified as shown in Eq. (25). Thus, from the above analysis, outage probability can be generally written as shown in Eq. (26). ...
... User information signals are coded and modulated by Quadrature phase shift key (QPSK) (CCSDS encoder [94]) and added together, then transmitted over a complex channel. In addition, various multipath fading channels such as AWGN, Rayleigh and Rician Channel [95][96][97] can also replace the dynamic channel. ...
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This Letter studies performance of a dual-hop decode-and-forward relaying network employing a wireless-powered relay antenna with transmit antenna selection for the first hop and maximal ratio combining for the second hop. Compact expressions for outage probability and upper-bound on channel capacity are derived. Monte Carlo simulation results are given to verify theoretical analyses. © 2018 Springer Science+Business Media, LLC, part of Springer Nature
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In this paper, the end-to-end bit error performance of a dual-hop (DH) energy harvesting (EH) amplify-and-forward/decode-and-forward (AF/DF) system is investigated. In this system, the source communicates with the destination over an intermediate relay when the direct link between the source and the destination is in deep fade. The channels are assumed to be exposed to Nakagami-m fading and all nodes are equipped with one antenna. The relay uses power splitting (PS) and time switching (TS) relaying protocols to harvest energy and uses it to forward the decoded signal or to transmit the amplified version of the received signal to the destination. The bit error probabilities (BEP) of the considered DH-AF and DH-DF systems are analytically derived for both EH protocols and their performances are comparatively evaluated. Moreover, a system optimization is performed to maximize the BER performance. For the TS mode, a list of mixture of modulations is provided for different spectral efficiency values and different time allocation parameters. Our comprehensive results on the BER performance of AF- and DF-aided DH networks with EH in the relay, provide basic guidelines for the design of future DH-EH systems.
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A decode-and-forward system with an energy-harvesting relay is analyzed for the case when an arbitrary number of independent interference signals affect the communication at both the relay and the destination nodes. The scenario in which the relay harvests energy from both the source and interference signals using a time switching scheme is analyzed. The analysis is performed for the interference-limited Nakagami-m fading environment, assuming a realistic nonlinearity for the electronic devices. The closed-form outage probability expression for the system with a nonlinear energy harvester is derived. An asymptotic expression valid for the case of a simpler linear harvesting model is also provided. The derived analytical results are corroborated by an independent simulation model. The impacts of the saturation threshold power, the energy-harvesting ratio, and the number and power of the interference signals on the system performance are analyzed.
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Energy efficiency will play a crucial role in future communication systems and has become a main design target for all 5G radio access networks. The high operational costs and impossibility of replacing or recharging wireless device batteries in multiple scenarios, such as wireless medical sensors inside the human body, call for a new technology by which wireless devices can harvest energy from the environment via capturing ambient RF signals. SWIPT has emerged as a powerful means to address this issue. In this article, we survey the current architectures and enabling technologies for SWIPT and identify technical challenges to implement SWIPT. Following an overview of enabling technologies for SWIPT and SWIPT-assisted wireless systems, we showcase a novel SWIPT-supported power allocation mechanism for D2D communications to illustrate the importance of the application of SWIPT. As an ending note, we point out some future research directions to encourage and motivate more research efforts on SWIPT.
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The outage probability of a decode-and-forward relaying system based on simultaneous wireless information and power transfer (SWIPT) in the presence of Nakagami fading is investigated. The relaying model considers both the source-destination direct link the the source-relay-destination link. The power splitter at the relaying device provides energy to the relay by splitting the received signal power into energy harvesting and information transfer parts. The derived outage expression is verified using simulation results. The results show an impressive amount of percentage decrease in outage probability for Nakagami fading with different values of shape parameter in comparison to Rayleigh fading.
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In this letter, we discuss multiple links with equal weights, in buffer size based relay selection schemes in cooperative wireless networks. A general relay selection factor is defined, which includes the weight of the link as the first metric and the link quality, or priority, as the second metric for different cases of the same weight. The Markov chain based theoretical framework is employed to evaluate the outage probability, delay and throughput of the system. The proposed scheme is evaluated for symmetric and asymmetric channel conditions. The link quality based second selection metric achieves lower outage probability, while the link priority based selection shows significant improvements in terms of delay and throughput. Theoretical results are validated through extensive Monte carlo simulations.
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In this paper, we study a cooperative wireless relay network (WRN) in which multiple source-destination pairs communicate via a decode-and-forward (DF) relay which harvests energy from the source transmissions in the presence of an interfering signal. The goal is to efficiently distribute the relay’s power among the different relay-destination (R � D) links. The outage probability and the throughput in the delay-sensitive transmission mode are derived for the non-shared and several shared power allocation schemes. Numerical results show that the studied shared allocation schemes outperform the non-shared allocation scheme in terms of outage probability and throughput. Different shared allocation schemes are compared against each other in terms of outage probability, throughput and fairness. The R � D channel dependent (RDCD) and the weighted-sumrate maximization (WSRM) schemes achieve the best outage and throughput performances but require knowledge of the statistical channel state information (CSI) at the relay node. The results also illustrate the trade-off between the throughput and the fairness of the different shared allocation schemes.
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Considering a dual-hop energy-harvesting (EH) relaying system, this paper advocates novel relaying protocols based on adaptive time-switching (TS) for amplify-and-forward and decode-and-forward modes, respectively. The optimal TS factor is first studied, which is adaptively adjusted based on the dualhop channel state information (CSI), accumulated energy and threshold signal-to-noise ratio (SNR), to achieve the maximum throughput efficiency per block. To reduce the CSI overhead at the EH relay, low-complexity TS factor design is presented which only needs single-hop CSI to determine the TS factor. Theoretical results show that, in comparison with the conventional solutions, the proposed optimal/low-complexity TS factor can achieve higher limiting throughput efficiency for sufficiently small threshold SNR. As the threshold SNR approaches infinity, the throughput efficiency of the proposed optimal/low-complexity TS factor tends to zero in a much slower pace than that of the conventional solutions. Simulation results are presented to corroborate the proposed methodology.
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In this paper, we consider two-hop multi-input multi-output relay wireless systems with energy harvesting. In each hop, transmit antenna selection/receive antenna selection, transmit antenna selection/maximum ratio combining, or maximum ratio transmission/receive antenna selection is used. Also, an energy-constrained relay harvests energy from the source via either a time switching–based relaying protocol or a power splitting–based relaying protocol. We perform unified analysis of the systems over Nakagami-m fading channels. Specifically, we derive exact closed form expressions for ergodic capacity and throughput (for delay-tolerant transmission mode) and outage probability and throughput (for delay-limited transmission). Optimal energy-harvesting time (in time switching–based relaying protocol–based system) and optimal power-splitting ratio (in power splitting–based relaying protocol–based system) to achieve maximum throughput at high signal-to-noise-ratio are also determined. Moreover, we derive an exact closed form expression for the bit error rate, which facilitates the evaluation of the system performance. Impacts of various multi-input multi-output processing schemes, numbers of equipped antennas, energy-harvesting mechanisms, and transmission modes on the system performance are also examined and discussed. All theoretical analyses are corroborated by simulations.
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In the work, a dual-hop cooperative simultaneous wireless information and power transfer (SWIPT) system, in which there are a source-destination ( ) pair and a relay node (R), is considered. R adopts threshold amplify-and-forward (AF)/decode-and-forward (DF) relaying schemes to decide whether to aid pair’s information transmission not. The effect of SWIPT on the outage performance has been investigated and the closed-form analytical expressions for outage probability have been derived for threshold AF and DF relaying schemes, respectively, which are verified by Monte-Carlo simulations.
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In this paper, we systematically study the performance of two and three time slot transmission schemes (2TS and 3TS) for bidirectional amplify-and-forward (AF) relaying channels, which are deployed by simultaneous wireless information and power transfer (SWIPT). In particular, in SWIPT, there are two protocols, namely power time splitting-based two-slot (PTSTW) and power time splitting-based three-slot (PTSTH) relaying protocol. We also derive closed-form expressions of throughput for both delay-limited and delay-tolerant transmission mode. Moreover, the proposed protocols will be evaluated in terms of the large scale path loss and the distance allocation to achieve the optimal throughput. In addition, numerical results prove that the throughput of PTSTW outperforms PTSTH. Furthermore, the throughput of delay-tolerant transmission mode is greatly better than delay-limited transmission mode. Other numerical results are also provided to verify the validity of theoretical analysis.
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Performance of wireless powered relay with amplify-and-forward protocol is studied for Nakagami-m fading channels. Different from the existing literature, we consider the nonlinearity of the energy harvester. An analytical expression is derived for the complementary cumulative distribution function (CCDF) of the end-to-end signal-to-noise ratio. Using the CCDF, outage capacity is calculated.
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Energy-harvesting relaying is a promising solution to the extra energy requirement at the relay. It can transfer energy from the source to the relay. This will encourage more idle nodes to be involved in relaying. In this paper, the outage probability and the throughput of an amplify-and-forward relaying system using energy harvesting are analyzed. Both time switching and power-splitting harvesting schemes are considered. The analysis takes into account both the Nakagami-m fading caused by signal propagation and the interference caused by other transmitters. Numerical results show that time switching is more sensitive to system parameters than power splitting. Also, the system performance is more sensitive to the transmission rate requirement, the signal-to-interference-plus-noise ratio in the first hop and the relaying method.