NOMA has emerged as a promising technique for enhancing capacity and performance in 5G mobile and wireless networks. By allowing multiple users to access the same frequency and time domains simultaneously, NOMA employs successive interference cancellation (SIC) to effectively separate all signals. This results in improved spectral efficiency. Unlike its counterpart, orthogonal multiple access (OMA), where users are classified based on recurrence, schedule, and code, NOMA classifies users based on power. To further optimize efficiency, this study examines two power allocation techniques. The first technique utilizes information on the channel states of NOMA users, while the second refers to pre-set quality of service (QoS) for each NOMA user.