Throughput Maximization & Power Optimization Analysis in Non-Orthogonal Multiple Access System

Abstract

Currently, non-orthogonal multiple access (NOMA) has been considered as a key authorizing multiple access scheme for 5G & beyond (B5G) cellular systems. In NOMA, by utilizing the variations in channels gain, multiple users can be multiplexed in power domain and then non-orthogonally organized for communication on the same spectrum resources. Practical successive interference cancellation (SIC) technique needs to be used at the receivers to decode the desired information signals. In this research, we formulate a downlink NOMA sum- throughput maximization problem in a cellular system such that power allocations for devices in NOMA cell can be optimized based on the transmitted power budget and Quality of service (QoS) constraints. Analysis for the objective function with the constraints to demonstrate the convexity of the optimization problem is presented. Lagrange multipliers and Karush-Kuhn-Tucker (KKT) optimality conditions are applied to derive the optimal power allocations. Simulations are conducted using Genetic algorithm (GA) solver to investigate the improvement achieved in power allocation using power optimization compared to the users with fixed power scenario in terms of bit error rate (BER), sum-rate, outage probability and SIC error.