International Conference on Computer and Knowledge Engineering

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Energy Efficient Power Allocation in MIMO-NOMA Systems with ZF Receiver Beamforming in Multiple Clusters

Authors :

Mahdi Nangir¹ Abdolrasoul Sakhaei Gharagezlou² Nima Imani³

1- Faculty of Electrical and Computer Engineering University of Tabriz 2- Faculty of Electrical and Computer Engineering University of Tabriz 3- Faculty of Electrical and Computer Engineering University of Tabriz

Keywords :

Multiple-Input Multiple-Output, Non-Orthogonal Multiple Access, Energy Efficiency, Power Allocation, Error Estimation, Zero Forcing Beamforming, KKT conditions.

Abstract :

This paper deals with the problem of energy efficient power allocation for a multiple-input multiple-output (MIMO) system with non-orthogonal multiple access (NOMA) method. The characteristics of the used channel are determinative in this system. Some key parameters that have not considered in most of the works, are examined in this paper, such as: the path loss, the zero forcing (ZF) beamforming, and the channel estimation error. In solving this problem, two constraints on the minimum user rate and the maximum transmission power of users are considered. The objective function of the optimization problem is the energy efficiency (EE) of the system, which is generally non-convex and constrained problem. First, it is converted to a convex problem using the convex optimization theory. Next, by employing the Lagrange dual function, the constraints of the problem are eliminated. By doing so, the problem becomes a convex unconstraint problem, and the Karush-Kuhn-Tucker (KKT) conditions are used to obtain the optimal power of the users. Furthermore, an iterative algorithm as a numerical solution is proposed for the problem. Our simulation results show that it outperforms the equal power allocation strategy.