# Wireless Energy Harvesting with Cooperative Relaying under the Best Relay Selection Scheme
## 2 Related Works
In the first scheme, the cooperating relays retransmit a weighted version of the source data in a DF fashion. The second scheme related to cooperative jamming (C)), while the source was transmitting, cooperating relays transmit weighted noise to confound the eavesdropper. In [32], SE was studied over a single EH relay with the adaptive transmission technique. In [33], the current contributions of the information and communication technology (ICT) system led to the release of about 5% of the carbon dioxide into the environment. Unfortunately, this percentage is increasing as the number of smart devices increase. To reduce the impact of \(CO_{2}\) energy emissions, efficient techniques need to evolve to design sustainable and eco-friendly wireless communication network [34]. Following this, EE was proposed as a metric to complement SE in evaluating the absolute transmission effectiveness of 5G cellular networks [35]. The best solution is to achieve the maximum EE and SE simultaneously, although mathematically, the metrics have proven to conflict with one another, such that the maximization of EE brings about poor performance in SE [36]. Research has shown that both EE and SE have joint consideration in achieving an efficient 5G wireless communication system in the future [37]. According to [38], EE converges to a constant, \([1/N_{o}ln2]\), when SE approaches zero (\(N_{o}\) is power spectral density of additive white Gaussian noise (AWGN)), while EE approaches zero as SE goes to infinity. The ideal relationship between SE and EE is illustrated in Figure 1. The circuit power will eliminate the monotonous relationship between SE and EE. If we take the circuit power into consideration, the SE-EE curve will become bell-shaped, as in Figure 1. Transmission features such as modulation scheme, transmission distance, and resource management are influential in the SE and EE trade-off [39]. An investigation into industrial approaches and telecommunication policies toward energy-efficient transmission will become a valuable addition; it is important for protecting the environment and promoting sustainable development for future wireless cellular systems. The authors of [40] illustrated the trade-off between performance and complexity for different combining schemes. The first scheme is defined as all relay participate (ARP), where the destination combines the received signals from all the relays, while the second scheme is known as BRS scheme, which used the relay that has the maximum signal to noise ratio (SNR) at the destination. In [41], a genetic algorithm (GA) is applied for the optimization of power splitting ratio at the relays over imperfect feedback channels. EH relaying system with link adaptation under an imperfect feedback channel was proposed in order to maximize the throughput to meet the main requirements in green wireless communication systems. The 5G innovation will soon fulfill numerous necessities, of which conveying high system energy performance is the most basic. This component is critical to decrease operational expense and give organized access in a practical and resource-efficient way. High energy performance requires a central change in outline standards inside the versatile telecom industry. The green radio networks aim to compensate for the increase in total energy consumption,  
Figure 1: Ideal case and Practical case. carbon footprint, and operational cost as a result from the increase in the number of base stations (BSs), which consume 57% of the total mobile network infrastructure energy [42]. Based on the previous approaches, it can be concluded that the EH relaying technique is a promising solution for achieving a green wireless system. In this paper, SE and EE of EH relaying are presented and compared with conventional relaying.