Abstract: Background: Communication has become an integral part of people lives and like any innovation, it faces the problem of energy efficiency due to new technologies and the number of growing users. Hence, initiatives are being taken to find solutions to this problem and to attain green communication which reduces the energy consumption and should not compromise on the Quality of Service (QoS). With the phenomenal increase in the number of users using cellular devices, it now becomes important to knock at green communication. Materials and Methods: In this study, an idea to bring out what green communication exactly aims at in the context of wireless communication and give an overview of the various approaches followed in implementation of green communication with emphasis on cognitive radio mechanism. It also focuses on the concept of Multiple Input Multiple Output (MIMO) technique that can be used in developing technologies and proves to be beneficial when compared to Single Input Single Output (SISO) or Multiple Input Single Output (MISO) when taking into consideration the energy efficiency of the system. Results: Comparison of different transmission models based on their BER, distance and energy consumption per bit were estimates. This simulation shows that the BER of MIMO is better than the other schemes and also the performance of MISO and SISO are comparable to each other. Bit Error Rate (BER) of MISO and SISO increases with distance, while that of MIMO remains relatively constant. A similar result is obtained when the energy consumption per bit is plotted with distance. From aforementioned simulation result, it can infer that MIMO proves to be advantageous with increasing the distance and that in some cases MISO performs better than SISO. Conclusion: This simulation gives the comparison based on the total energy consumption per bit, which includes the circuit power consumption of the transmitter and receiver. This simulation clearly shows that MIMO concept should be used when the distance used is longer.