# Wireless Energy Harvesting with Cooperative Relaying under the Best Relay Selection Scheme
## 2 Related Works  
The authors of [14] presented two schemes for wireless information and power transfer: Power Splitting (PS) and Time Switching (TS). In the PS scheme, the receiver divides the signal power into two parts for harvesting energy and decoding information, while the receiver switches between two parts in the TS scheme. The authors of [15] proposed a joint analysis of the EE and SE trade-off, involving issues such as the multi-objective optimization problem (MOP). The parameters for the trade-off in the MOP change dramatically among various scenarios of communication considering different design requirements. MOP was transformed into a single-objective optimization problem (SOP) using a weighted sum algorithm, and the authors thus were able to achieve an optimal solution. In solving SOP, the harness was found as a result of the combination of channel allocation indicators. A multi-hop wireless network consisting of the DF relay was considered in [16]. Three SWIPT general protocols were considered in this paper: TS, PS, and hybrid protocol. In each protocol, an optimization problem was formulated to decide the optimal TS and PS ratios to maximize end-to-end throughput. A best cooperative mechanism for EE and wireless spectrum sharing within 5G systems was proposed in [17]. Data were transferred, and EE was derived during the transmission mode of the intended timeslot. EH within the best cooperative mechanism was simultaneously conducted by primary users (PUs) and secondary users (SUs) from ambient signals. A short time duration with the BCM was allowed to transfer data throughout the time slot. Optimization problems were then formulated with the best cooperative mechanism model. The purpose of the optimization was to maximize the throughput for PUs and SUs under the EE metric and data rate. In [2], an approximate mathematical expression for symbol error probability within cooperative communication systems by means of best relay selection was derived over channels of Nakagami-m fading type with independent and non-identically distributed (i.ni.d) links. In the case of AF relaying protocol, the best instantaneous SNR corresponding to the relaying link is provided by the selected relay. Differently, in the case of DF, the selected relay offers the most excellent instantaneous SNR corresponding to the link that connects the destination and the relay from the relays that have decoded the source information correctly. Joint power allocation and relay selection schemes for throughput maximization were proposed in [18] for the AF cooperative network, in which the relay and source are EH nodes. The optimal selection of the relay depends on the amount of harvested energy stored within the SNR of the nodes and channel. Offline schemes are important in case the amount of energy harvested and the SNR of the channel are given a priori, which is impossible due to the random nature of these values. As an application of EH, the authors of [19] proposed a multi-dimensional sparse-coded ambient backscatter communication system for the high-rate massive Internet of Things (IoT) networks. RF tags were considered to increase the dimension of the signal space of backscatter signals to achieve high diversity gains. The authors guaranteed sufficient energy harvesting opportunities at RF tags. Another alternative power source from the wireless transmission can be exploited by the use of near-field wireless power transfer (WPT), as presented in [20]. WPT has been used in mobile phones, electric vehicles, medical implants and wireless sensor network. The authors provided recent studies for near-field WPT for potential applications in the real world. Within wireless-powered communication networks (WPCNs), it is essential to search for the fairness of EE to investigate the node balance for harvesting energy and receiving information. In [21], an efficient iterative method was proposed for the fairness of optimal EE within WPCNs.