Improving Jain Fairness Index and Optimizing Transmitter Power Consumption in NOMA Systems.

In this paper, an approach is proposed for power allocation in Non-orthogonal multiple access (NOMA) systems in downlink to achieve user fairness from user capacity perspective and to optimize transmitter power consumption as well. In recent works, researchers have defined optimization problems and solved them, as in a method called Fair-NOMA, to maximize the capacity of each user in NOMA compared to OMA but the difference between the capacity of users and optimizing the transmitter power consumption are not considered. In this paper, a NOMA system with 2 and more than 2 users in downlink is considered. In the 2-user scenario by equating capacities of users, the Jain fairness index is maximized, fairness is achieved in transmitter power consumption and the difference between the capacities of users is eliminated. In addition, computer simulations show that the capacity of the user with weaker channel gain improves noticeably. Moreover, in a NOMA system with more than 2 users a fixed power coefficient is allocated to the user with the weakest channel condition, and power allocation to the other users is done in a way that the transmitter power consumption is optimized. Computer simulations is carried out to verify the effectiveness of the suggested methods.