An innovative markov-driven power allocation mechanisms for HARQ-Enhanced MIMO-NOMA System in 5G Networks and Beyond

• This work examines one type of NOMA, wherein various simultaneous broadcasts with varying transmission powers are permitted over the same channel. • This work considers and explores a HARQ-aided NOMA-MIMO communication system following an effective Markov-based method. • The system performance is then examined using this model by studying OP at each user in the system and ER required to correctly deliver sent messages to their destinations with various transmission power levels. • Studying power allocation in such system is not straight forward; according to our knowledge, no previous research considered such study. • We demonstrate the simplicity, tractability, and accuracy of our Markov-based method and consequently verify the correctness of this method through simulations. In the context of the fifth generation (5G) system, the non-orthogonal multiple-access (NOMA) technique has proposed to be an effective option for increasing the efficiency of the spectral. This work examines one type of NOMA, wherein various simultaneous broadcasts with varying transmission powers are permitted over the same channel. The integration of hybrid-automated repeat-request (HARQ) scheme with multiple-input multiple-output (MIMO) system can enhance the performance of NOMA. In this research, we consider and explore a HARQ-aided NOMA-MIMO communication system following an effective Markov-based method. More specifically, we consider a discrete-time Markov chain (DTMC) to represent this system. The system performance is then examined using this model by studying the outage probability (OP) at each user in the system and the expected number of retransmissions (ER) required to correctly deliver sent messages to their destinations with various transmission power levels. Remarkably, studying power allocation (PA) in such system is not straight forward; according to our knowledge, no previous research considered such study. Accordingly, in this research, we propose two efficient Markov-based PA approaches for HARQ-aided NOMA-MIMO system. Interestingly, we demonstrate the simplicity, tractability, and accuracy of our Markov-based method in studying the considered system. Using simulations, we show that integrating HARQ into MIMO-NOMA substantially reduces the OP at each part of the system and we show that PA significantly reduces OP; it is nearly zero at some users. Moreover, we verify the efficiency of the proposed PA approaches.