# Game Theory-Based Smart Mobile-Data Offloading Scheme in 5G Cellular Networks
## 1 Introduction
In recent works, wireless communications powered by external harvested energy has become a promising technique to deal with the energy-constraint problem. As a normal wireless node, a wireless device has a finite-capacity battery that can be recharged from ambient radio frequency (RF) signals and used for operations such as data processing and data transmission. The battery of a wireless device will store harvested energy without manually changing or recharging it. Recently, rectifying antenna design has become more efficient at harvesting energy from RF signals [18, 19]. The RF signal comes from various sources such as wireless internet, radio stations, satellite stations, and digital multimedia broadcasting. Although the RF signal is abundant in space and can be retrieved without limit, there are still many unresolved problems of RF energy harvesting (RF-EH) in practical. One of practical issue related to RF-EH is hardware design for RF energy harvesters such as antenna with a large aperture, impedance matching circuit, rectifier, and voltage multiplier [20, 21]. In addition to collecting energy from the ambient RF, the RF-EH device can also actively request energy from associated base stations and access points in some applications. In this case, the influence of the data flow and the energy flow on communication process is complicated due to interference of the energy transmission with the information decoding or interruption of the energy reception in the information transmission process [22]. Along with RF-EH, non-RF energy resources (solar, wind, etc.) can provide perpetual energy and higher power density for rechargeable batteries of wireless users [23, 24]. Therefore, in this paper, we consider non-RF energy harvesting (NRF-EH) as one of the mobile-user controlled parameters that affect network performance. In this paper, we study the problem of MDO via D2D links. Specifically, we consider an offloading scenario where one UE offloads its cellular traffic to another UE. Figure 1 provides an example of offloading in cellular networks where the hexagon denotes the coverage area of the CNO's macrocell and the interference among UEs is considered in the transmission process. In the data offload case,data transmission between UEs can be made as follows: First, the source UE can offload some traffic to destination UE with an offload coefficient if D2D link is available, which is denoted as \"the solid arrow\" in the Figure 1. After that, the remaining data traffic of source UE will be transferred to the destination UE via BS, which is denoted as \"dashed arrow\". On the other hand, in the no-offload case, the data of source UE can be transmitted to destination UE only through BS-based transmission, and the offload coefficient will be zero. In Figure 1, UE1, UE2, and UE4 are source UE while UE3, UE5, and UE6 are destination UE. Even though Figure 1 shows 6 UEs case as an example. However, without loss of generality, the system model can be applied to 5G cellular networks. In such an offloading model, we are interested in the following issues: 1) How to offload data efficiently in terms of maximizing throughput and EE, and 2) How to equalize the offloading benefits among D2D links in the network. To do this, in the paper, we model and analyze the data offloading problem by using the NBS and Jain's fairness index. The main contributions of this paper are summarized as follows:  
* We consider the problem of MDO in NRF-EH environments, where UEs can simultaneously harvest non-RF energy from the ambient environment (e.g., solar power) and execute data communications with other UEs via the path-loss model with a log normal distribution of shadow fading. * We evaluate the performance of the schemes via MATLAB simulation under various network in terms of the fairness, throughput, and EE. In particular, a fairness based on Jain fairness index [25] is considered.