Context: The usage of cellular devices has been advanced in recent years and expected to increase rapidly in the coming years. Thanks to rapid development of technologies which is making us comfortable in the field of communications. The rapid development in technology is causing many serious hazards to the environment and also the mobile operators are facing problems with increasing energy costs and regulatory pressures to reduce carbon footprint to operate Green networks. Objectives: This research provides a study on the problems pertaining to energy efficiency and remedies to overcome issues in decreasing energy efficiency of networks, this research also concentrates on various approaches for energy efficiency in base stations, the goal is to identify the best technologies that best suits the base station platform in terms of energy efficiency. Methods: Two different methods are carried out throughout our research • Literature Review In this literature review problems pertaining to energy efficiency of base stations are studied and reported, there by different technologies which helps to increase energy efficiency of base stations are analysed and best technologies are reported. • Experimentation This section describes the concept of cognitive radio. It helps in energy efficiency in a cognitive network through analysis of two routing protocols AODV and OLSR using NS2 simulator. Results: • From the literature review we look at the energy consumptions issues of base stations (RQ1). • For RQ2, the remedies to reduce energy consumption are studied and the best suitable technologies for energy efficiency are suggested. • For answering RQ3, experimentation is carried out concentrating on achieving energy efficiency through cognitive radio network. Conclusions: Thus, Problems pertaining to energy efficiency of base stations are studied, and best technologies to reduce energy consumption of base stations are reported. Comparison of two routing protocols OLSR and AODV under cognitive radio is also studied proposing the best routing protocol.