# Optimal Design of a Hybrid Solar PV/BG-Powered Heterogeneous Network
## 2 Literature Review  
A growing interest in research is the effective use of renewable energy in cellular mobile technology. In addition, the future mobile industry will be strongly affected by the massive IoT devices deployment. Authors in [19; 20] presented a solar PV-powered mobile base station in conjunction with sufficient energy storage devices. The technical and economic feasibility of the solar PV-powered cellular network has been examined thoroughly, taking into consideration the variation of solar radiation and traffic. In References [21; 22], the authors used the HOMER platform to find the best system design and technical criteria for deploying hybrid solar PV/diesel generator (DG)-powered off-grid BSs across the world. The integration of solar PV with DG might reduce renewable energy output variations and increase the quality of service, but it partially increases DG-related issues, including high fuel prices, operation, and maintenance costs (OMC), and carbon emissions. In addition, fuel transfer to the DG is not economically efficient in remote regions. The combined utilization of multiple sources to achieve a sustainable and reliable energy source for BSs has been investigated in [23; 24; 25]. For a non-grid homogenous cellular network, a hybrid solar PV with a biomass generator (BG) supply scheme was developed in [26]. The integration of solar PV with biomass resources for establishing a long-term sustainable and reliable power station has been thoroughly investigated in reference [27]. In this work, the fundamental problems of developing a hybrid solar PV/biomass-focused power plant were investigated, and several significant solutions were proposed. A hybrid solar PV/wind turbine (WT)-powered macro-BS has been suggested in [28] considering the dynamic profile of renewable energy sources in Bangladesh. The works [25] and [29] employ a network with and without an energy sharing framework for the installation of the hybrid solar PV and WT-enabled homogenous network. Combining renewable energy with storage devices can improve reliability and minimize the energy gap between demand and supply, as shown in reference [30]. Being inspired by the potential benefits of renewable energy, Nokia Siemens has installed a hybrid solar PV/WT-powered base station in an urban location in Germany [31]. In References [29; 32; 33], energy sharing among neighboring base stations has been employed using resistive power lines or the intelligent grid. Average energy affinity (AEA) and stochastic energy affinity (SEA) measures are used to develop agglomerative and divisive hierarchical clustering algorithms to provide BSs with an energy-sharing model [29]. To achieve a fair decrease in energy usage and emissions of GHGs, a renewable energy-based community energy plan has been developed in [34]. In [35], the researchers reportedan optimal common solar PV framework throughout society. Reference [32] proposes an optimum energy cooperation architecture among cellular BSs, which incorporates both renewable energy and grids via physically linked resistive power lines. A macro-BS energy collaboration model is shown in reference [33]. According to the aforementioned research articles, onsite green energy exchange amongst BSs is cost-effective and sustainable. Traditional macrocell designs are often built to cater to broader spectral regions, which frequently fail to provide the throughput required to provide smooth broadband service to uplink customers. Furthermore, users often move away from the macro-BS, causing significant inter-cell interference. Under the typical macrocell scenario, the lack of interior infiltration and the formation of dead patches significantly limit indoor coverage. Heterogeneous networks provide considerable network performance leaps through larger network capacity and improved coverage as a potential way to tackle these difficulties [4; 5; 36]. HetNet is a multi-tier cellular network in which macro-base stations serve as mother base stations and offer a consistent coverage area.